Bundle relevant parts of sqlite 2.8.0.

# sqlite has a completely non-restrictive license

1 files changed, 2347 insertions, 0 deletions

diff --git a/ext/sqlite/libsqlite/src/select.c b/ext/sqlite/libsqlite/src/select.c
new file mode 100644
index 0000000000..03eb861c9e
--- /dev/null
+++ b/ext/sqlite/libsqlite/src/select.c
@@ -0,0 +1,2347 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle SELECT statements in SQLite.
+**
+** $Id$
+*/
+#include "sqliteInt.h"
+
+
+/*
+** Allocate a new Select structure and return a pointer to that
+** structure.
+*/
+Select *sqliteSelectNew(
+  ExprList *pEList,     /* which columns to include in the result */
+  SrcList *pSrc,        /* the FROM clause -- which tables to scan */
+  Expr *pWhere,         /* the WHERE clause */
+  ExprList *pGroupBy,   /* the GROUP BY clause */
+  Expr *pHaving,        /* the HAVING clause */
+  ExprList *pOrderBy,   /* the ORDER BY clause */
+  int isDistinct,       /* true if the DISTINCT keyword is present */
+  int nLimit,           /* LIMIT value.  -1 means not used */
+  int nOffset           /* OFFSET value.  -1 means not used */
+){
+  Select *pNew;
+  pNew = sqliteMalloc( sizeof(*pNew) );
+  if( pNew==0 ){
+    sqliteExprListDelete(pEList);
+    sqliteSrcListDelete(pSrc);
+    sqliteExprDelete(pWhere);
+    sqliteExprListDelete(pGroupBy);
+    sqliteExprDelete(pHaving);
+    sqliteExprListDelete(pOrderBy);
+  }else{
+    pNew->pEList = pEList;
+    pNew->pSrc = pSrc;
+    pNew->pWhere = pWhere;
+    pNew->pGroupBy = pGroupBy;
+    pNew->pHaving = pHaving;
+    pNew->pOrderBy = pOrderBy;
+    pNew->isDistinct = isDistinct;
+    pNew->op = TK_SELECT;
+    pNew->nLimit = nLimit;
+    pNew->nOffset = nOffset;
+  }
+  return pNew;
+}
+
+/*
+** Given 1 to 3 identifiers preceeding the JOIN keyword, determine the
+** type of join.  Return an integer constant that expresses that type
+** in terms of the following bit values:
+**
+**     JT_INNER
+**     JT_OUTER
+**     JT_NATURAL
+**     JT_LEFT
+**     JT_RIGHT
+**
+** A full outer join is the combination of JT_LEFT and JT_RIGHT.
+**
+** If an illegal or unsupported join type is seen, then still return
+** a join type, but put an error in the pParse structure.
+*/
+int sqliteJoinType(Parse *pParse, Token *pA, Token *pB, Token *pC){
+  int jointype = 0;
+  Token *apAll[3];
+  Token *p;
+  static struct {
+    const char *zKeyword;
+    int nChar;
+    int code;
+  } keywords[] = {
+    { "natural", 7, JT_NATURAL },
+    { "left",    4, JT_LEFT|JT_OUTER },
+    { "right",   5, JT_RIGHT|JT_OUTER },
+    { "full",    4, JT_LEFT|JT_RIGHT|JT_OUTER },
+    { "outer",   5, JT_OUTER },
+    { "inner",   5, JT_INNER },
+    { "cross",   5, JT_INNER },
+  };
+  int i, j;
+  apAll[0] = pA;
+  apAll[1] = pB;
+  apAll[2] = pC;
+  for(i=0; i<3 && apAll[i]; i++){
+    p = apAll[i];
+    for(j=0; j<sizeof(keywords)/sizeof(keywords[0]); j++){
+      if( p->n==keywords[j].nChar 
+          && sqliteStrNICmp(p->z, keywords[j].zKeyword, p->n)==0 ){
+        jointype |= keywords[j].code;
+        break;
+      }
+    }
+    if( j>=sizeof(keywords)/sizeof(keywords[0]) ){
+      jointype |= JT_ERROR;
+      break;
+    }
+  }
+  if(
+     (jointype & (JT_INNER|JT_OUTER))==(JT_INNER|JT_OUTER) ||
+     (jointype & JT_ERROR)!=0
+  ){
+    static Token dummy = { 0, 0 };
+    char *zSp1 = " ", *zSp2 = " ";
+    if( pB==0 ){ pB = &dummy; zSp1 = 0; }
+    if( pC==0 ){ pC = &dummy; zSp2 = 0; }
+    sqliteSetNString(&pParse->zErrMsg, "unknown or unsupported join type: ", 0,
+       pA->z, pA->n, zSp1, 1, pB->z, pB->n, zSp2, 1, pC->z, pC->n, 0);
+    pParse->nErr++;
+    jointype = JT_INNER;
+  }else if( jointype & JT_RIGHT ){
+    sqliteSetString(&pParse->zErrMsg, 
+      "RIGHT and FULL OUTER JOINs are not currently supported", 0);
+    pParse->nErr++;
+    jointype = JT_INNER;
+  }
+  return jointype;
+}
+
+/*
+** Return the index of a column in a table.  Return -1 if the column
+** is not contained in the table.
+*/
+static int columnIndex(Table *pTab, const char *zCol){
+  int i;
+  for(i=0; i<pTab->nCol; i++){
+    if( sqliteStrICmp(pTab->aCol[i].zName, zCol)==0 ) return i;
+  }
+  return -1;
+}
+
+/*
+** Add a term to the WHERE expression in *ppExpr that requires the
+** zCol column to be equal in the two tables pTab1 and pTab2.
+*/
+static void addWhereTerm(
+  const char *zCol,        /* Name of the column */
+  const Table *pTab1,      /* First table */
+  const Table *pTab2,      /* Second table */
+  Expr **ppExpr            /* Add the equality term to this expression */
+){
+  Token dummy;
+  Expr *pE1a, *pE1b, *pE1c;
+  Expr *pE2a, *pE2b, *pE2c;
+  Expr *pE;
+
+  dummy.z = zCol;
+  dummy.n = strlen(zCol);
+  dummy.dyn = 0;
+  pE1a = sqliteExpr(TK_ID, 0, 0, &dummy);
+  pE2a = sqliteExpr(TK_ID, 0, 0, &dummy);
+  dummy.z = pTab1->zName;
+  dummy.n = strlen(dummy.z);
+  pE1b = sqliteExpr(TK_ID, 0, 0, &dummy);
+  dummy.z = pTab2->zName;
+  dummy.n = strlen(dummy.z);
+  pE2b = sqliteExpr(TK_ID, 0, 0, &dummy);
+  pE1c = sqliteExpr(TK_DOT, pE1b, pE1a, 0);
+  pE2c = sqliteExpr(TK_DOT, pE2b, pE2a, 0);
+  pE = sqliteExpr(TK_EQ, pE1c, pE2c, 0);
+  ExprSetProperty(pE, EP_FromJoin);
+  if( *ppExpr ){
+    *ppExpr = sqliteExpr(TK_AND, *ppExpr, pE, 0);
+  }else{
+    *ppExpr = pE;
+  }
+}
+
+/*
+** Set the EP_FromJoin property on all terms of the given expression.
+**
+** The EP_FromJoin property is used on terms of an expression to tell
+** the LEFT OUTER JOIN processing logic that this term is part of the
+** join restriction specified in the ON or USING clause and not a part
+** of the more general WHERE clause.  These terms are moved over to the
+** WHERE clause during join processing but we need to remember that they
+** originated in the ON or USING clause.
+*/
+static void setJoinExpr(Expr *p){
+  while( p ){
+    ExprSetProperty(p, EP_FromJoin);
+    setJoinExpr(p->pLeft);
+    p = p->pRight;
+  } 
+}
+
+/*
+** This routine processes the join information for a SELECT statement.
+** ON and USING clauses are converted into extra terms of the WHERE clause.
+** NATURAL joins also create extra WHERE clause terms.
+**
+** This routine returns the number of errors encountered.
+*/
+static int sqliteProcessJoin(Parse *pParse, Select *p){
+  SrcList *pSrc;
+  int i, j;
+  pSrc = p->pSrc;
+  for(i=0; i<pSrc->nSrc-1; i++){
+    struct SrcList_item *pTerm = &pSrc->a[i];
+    struct SrcList_item *pOther = &pSrc->a[i+1];
+
+    if( pTerm->pTab==0 || pOther->pTab==0 ) continue;
+
+    /* When the NATURAL keyword is present, add WHERE clause terms for
+    ** every column that the two tables have in common.
+    */
+    if( pTerm->jointype & JT_NATURAL ){
+      Table *pTab;
+      if( pTerm->pOn || pTerm->pUsing ){
+        sqliteSetString(&pParse->zErrMsg, "a NATURAL join may not have "
+           "an ON or USING clause", 0);
+        pParse->nErr++;
+        return 1;
+      }
+      pTab = pTerm->pTab;
+      for(j=0; j<pTab->nCol; j++){
+        if( columnIndex(pOther->pTab, pTab->aCol[j].zName)>=0 ){
+          addWhereTerm(pTab->aCol[j].zName, pTab, pOther->pTab, &p->pWhere);
+        }
+      }
+    }
+
+    /* Disallow both ON and USING clauses in the same join
+    */
+    if( pTerm->pOn && pTerm->pUsing ){
+      sqliteSetString(&pParse->zErrMsg, "cannot have both ON and USING "
+        "clauses in the same join", 0);
+      pParse->nErr++;
+      return 1;
+    }
+
+    /* Add the ON clause to the end of the WHERE clause, connected by
+    ** and AND operator.
+    */
+    if( pTerm->pOn ){
+      setJoinExpr(pTerm->pOn);
+      if( p->pWhere==0 ){
+        p->pWhere = pTerm->pOn;
+      }else{
+        p->pWhere = sqliteExpr(TK_AND, p->pWhere, pTerm->pOn, 0);
+      }
+      pTerm->pOn = 0;
+    }
+
+    /* Create extra terms on the WHERE clause for each column named
+    ** in the USING clause.  Example: If the two tables to be joined are 
+    ** A and B and the USING clause names X, Y, and Z, then add this
+    ** to the WHERE clause:    A.X=B.X AND A.Y=B.Y AND A.Z=B.Z
+    ** Report an error if any column mentioned in the USING clause is
+    ** not contained in both tables to be joined.
+    */
+    if( pTerm->pUsing ){
+      IdList *pList;
+      int j;
+      assert( i<pSrc->nSrc-1 );
+      pList = pTerm->pUsing;
+      for(j=0; j<pList->nId; j++){
+        if( columnIndex(pTerm->pTab, pList->a[j].zName)<0 ||
+            columnIndex(pOther->pTab, pList->a[j].zName)<0 ){
+          sqliteSetString(&pParse->zErrMsg, "cannot join using column ",
+            pList->a[j].zName, " - column not present in both tables", 0);
+          pParse->nErr++;
+          return 1;
+        }
+        addWhereTerm(pList->a[j].zName, pTerm->pTab, pOther->pTab, &p->pWhere);
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** This routine implements a minimal Oracle8 join syntax immulation.
+** The precise oracle8 syntax is not implemented - it is easy enough
+** to get this routine confused.  But this routine does make it possible
+** to write a single SQL statement that does a left outer join in both
+** oracle8 and in SQLite.
+**
+** This routine looks for TK_COLUMN expression nodes that are marked
+** with the EP_Oracle8Join property.  Such nodes are generated by a
+** column name (either "column" or "table.column") that is followed by
+** the special "(+)" operator.  If the table of the column marked with
+** the (+) operator is the second are subsequent table in a join, then
+** that table becomes the left table in a LEFT OUTER JOIN.  The expression
+** that uses that table becomes part of the ON clause for the join.
+**
+** It is important to enphasize that this is not exactly how oracle8
+** works.  But it is close enough so that one can construct queries that
+** will work correctly for both SQLite and Oracle8.
+*/
+static int sqliteOracle8JoinFixup(
+  int base,         /* VDBE cursor number for first table in pSrc */
+  SrcList *pSrc,    /* List of tables being joined */
+  Expr *pWhere      /* The WHERE clause of the SELECT statement */
+){
+  int rc = 0;
+  if( ExprHasProperty(pWhere, EP_Oracle8Join) && pWhere->op==TK_COLUMN ){
+    int idx = pWhere->iTable - base;
+    assert( idx>=0 && idx<pSrc->nSrc );
+    if( idx>0 ){
+      pSrc->a[idx-1].jointype &= ~JT_INNER;
+      pSrc->a[idx-1].jointype |= JT_OUTER|JT_LEFT;
+      return 1;
+    }
+  }
+  if( pWhere->pRight ){
+    rc = sqliteOracle8JoinFixup(base, pSrc, pWhere->pRight);
+  }
+  if( pWhere->pLeft ){
+    rc |= sqliteOracle8JoinFixup(base, pSrc, pWhere->pLeft);
+  }
+  if( pWhere->pList ){
+    int i;
+    ExprList *pList = pWhere->pList;
+    for(i=0; i<pList->nExpr && rc==0; i++){
+      rc |= sqliteOracle8JoinFixup(base, pSrc, pList->a[i].pExpr);
+    }
+  }
+  if( rc==1 && (pWhere->op==TK_AND || pWhere->op==TK_EQ) ){
+    setJoinExpr(pWhere);
+    rc = 0;
+  }
+  return rc;
+}
+
+/*
+** Delete the given Select structure and all of its substructures.
+*/
+void sqliteSelectDelete(Select *p){
+  if( p==0 ) return;
+  sqliteExprListDelete(p->pEList);
+  sqliteSrcListDelete(p->pSrc);
+  sqliteExprDelete(p->pWhere);
+  sqliteExprListDelete(p->pGroupBy);
+  sqliteExprDelete(p->pHaving);
+  sqliteExprListDelete(p->pOrderBy);
+  sqliteSelectDelete(p->pPrior);
+  sqliteFree(p->zSelect);
+  sqliteFree(p);
+}
+
+/*
+** Delete the aggregate information from the parse structure.
+*/
+static void sqliteAggregateInfoReset(Parse *pParse){
+  sqliteFree(pParse->aAgg);
+  pParse->aAgg = 0;
+  pParse->nAgg = 0;
+  pParse->useAgg = 0;
+}
+
+/*
+** Insert code into "v" that will push the record on the top of the
+** stack into the sorter.
+*/
+static void pushOntoSorter(Parse *pParse, Vdbe *v, ExprList *pOrderBy){
+  char *zSortOrder;
+  int i;
+  zSortOrder = sqliteMalloc( pOrderBy->nExpr + 1 );
+  if( zSortOrder==0 ) return;
+  for(i=0; i<pOrderBy->nExpr; i++){
+    int order = pOrderBy->a[i].sortOrder;
+    int type;
+    int c;
+    if( (order & SQLITE_SO_TYPEMASK)==SQLITE_SO_TEXT ){
+      type = SQLITE_SO_TEXT;
+    }else if( (order & SQLITE_SO_TYPEMASK)==SQLITE_SO_NUM ){
+      type = SQLITE_SO_NUM;
+    }else if( pParse->db->file_format>=4 ){
+      type = sqliteExprType(pOrderBy->a[i].pExpr);
+    }else{
+      type = SQLITE_SO_NUM;
+    }
+    if( (order & SQLITE_SO_DIRMASK)==SQLITE_SO_ASC ){
+      c = type==SQLITE_SO_TEXT ? 'A' : '+';
+    }else{
+      c = type==SQLITE_SO_TEXT ? 'D' : '-';
+    }
+    zSortOrder[i] = c;
+    sqliteExprCode(pParse, pOrderBy->a[i].pExpr);
+  }
+  zSortOrder[pOrderBy->nExpr] = 0;
+  sqliteVdbeAddOp(v, OP_SortMakeKey, pOrderBy->nExpr, 0);
+  sqliteVdbeChangeP3(v, -1, zSortOrder, strlen(zSortOrder));
+  sqliteFree(zSortOrder);
+  sqliteVdbeAddOp(v, OP_SortPut, 0, 0);
+}
+
+/*
+** This routine adds a P3 argument to the last VDBE opcode that was
+** inserted. The P3 argument added is a string suitable for the 
+** OP_MakeKey or OP_MakeIdxKey opcodes.  The string consists of
+** characters 't' or 'n' depending on whether or not the various
+** fields of the key to be generated should be treated as numeric
+** or as text.  See the OP_MakeKey and OP_MakeIdxKey opcode
+** documentation for additional information about the P3 string.
+** See also the sqliteAddIdxKeyType() routine.
+*/
+void sqliteAddKeyType(Vdbe *v, ExprList *pEList){
+  int nColumn = pEList->nExpr;
+  char *zType = sqliteMalloc( nColumn+1 );
+  int i;
+  if( zType==0 ) return;
+  for(i=0; i<nColumn; i++){
+    zType[i] = sqliteExprType(pEList->a[i].pExpr)==SQLITE_SO_NUM ? 'n' : 't';
+  }
+  zType[i] = 0;
+  sqliteVdbeChangeP3(v, -1, zType, nColumn);
+  sqliteFree(zType);
+}
+
+/*
+** This routine generates the code for the inside of the inner loop
+** of a SELECT.
+**
+** If srcTab and nColumn are both zero, then the pEList expressions
+** are evaluated in order to get the data for this row.  If nColumn>0
+** then data is pulled from srcTab and pEList is used only to get the
+** datatypes for each column.
+*/
+static int selectInnerLoop(
+  Parse *pParse,          /* The parser context */
+  Select *p,              /* The complete select statement being coded */
+  ExprList *pEList,       /* List of values being extracted */
+  int srcTab,             /* Pull data from this table */
+  int nColumn,            /* Number of columns in the source table */
+  ExprList *pOrderBy,     /* If not NULL, sort results using this key */
+  int distinct,           /* If >=0, make sure results are distinct */
+  int eDest,              /* How to dispose of the results */
+  int iParm,              /* An argument to the disposal method */
+  int iContinue,          /* Jump here to continue with next row */
+  int iBreak              /* Jump here to break out of the inner loop */
+){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+
+  if( v==0 ) return 0;
+  assert( pEList!=0 );
+
+  /* If there was a LIMIT clause on the SELECT statement, then do the check
+  ** to see if this row should be output.
+  */
+  if( pOrderBy==0 ){
+    if( p->nOffset>0 ){
+      int addr = sqliteVdbeCurrentAddr(v);
+      sqliteVdbeAddOp(v, OP_MemIncr, p->nOffset, addr+2);
+      sqliteVdbeAddOp(v, OP_Goto, 0, iContinue);
+    }
+    if( p->nLimit>=0 ){
+      sqliteVdbeAddOp(v, OP_MemIncr, p->nLimit, iBreak);
+    }
+  }
+
+  /* Pull the requested columns.
+  */
+  if( nColumn>0 ){
+    for(i=0; i<nColumn; i++){
+      sqliteVdbeAddOp(v, OP_Column, srcTab, i);
+    }
+  }else{
+    nColumn = pEList->nExpr;
+    for(i=0; i<pEList->nExpr; i++){
+      sqliteExprCode(pParse, pEList->a[i].pExpr);
+    }
+  }
+
+  /* If the DISTINCT keyword was present on the SELECT statement
+  ** and this row has been seen before, then do not make this row
+  ** part of the result.
+  */
+  if( distinct>=0 && pEList && pEList->nExpr>0 ){
+#if NULL_ALWAYS_DISTINCT
+    sqliteVdbeAddOp(v, OP_IsNull, -pEList->nExpr, sqliteVdbeCurrentAddr(v)+7);
+#endif
+    sqliteVdbeAddOp(v, OP_MakeKey, pEList->nExpr, 1);
+    if( pParse->db->file_format>=4 ) sqliteAddKeyType(v, pEList);
+    sqliteVdbeAddOp(v, OP_Distinct, distinct, sqliteVdbeCurrentAddr(v)+3);
+    sqliteVdbeAddOp(v, OP_Pop, pEList->nExpr+1, 0);
+    sqliteVdbeAddOp(v, OP_Goto, 0, iContinue);
+    sqliteVdbeAddOp(v, OP_String, 0, 0);
+    sqliteVdbeAddOp(v, OP_PutStrKey, distinct, 0);
+  }
+
+  switch( eDest ){
+    /* In this mode, write each query result to the key of the temporary
+    ** table iParm.
+    */
+    case SRT_Union: {
+      sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, NULL_ALWAYS_DISTINCT);
+      sqliteVdbeAddOp(v, OP_String, 0, 0);
+      sqliteVdbeAddOp(v, OP_PutStrKey, iParm, 0);
+      break;
+    }
+
+    /* Store the result as data using a unique key.
+    */
+    case SRT_Table:
+    case SRT_TempTable: {
+      sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, 0);
+      if( pOrderBy ){
+        pushOntoSorter(pParse, v, pOrderBy);
+      }else{
+        sqliteVdbeAddOp(v, OP_NewRecno, iParm, 0);
+        sqliteVdbeAddOp(v, OP_Pull, 1, 0);
+        sqliteVdbeAddOp(v, OP_PutIntKey, iParm, 0);
+      }
+      break;
+    }
+
+    /* Construct a record from the query result, but instead of
+    ** saving that record, use it as a key to delete elements from
+    ** the temporary table iParm.
+    */
+    case SRT_Except: {
+      int addr;
+      addr = sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, NULL_ALWAYS_DISTINCT);
+      sqliteVdbeAddOp(v, OP_NotFound, iParm, addr+3);
+      sqliteVdbeAddOp(v, OP_Delete, iParm, 0);
+      break;
+    }
+
+    /* If we are creating a set for an "expr IN (SELECT ...)" construct,
+    ** then there should be a single item on the stack.  Write this
+    ** item into the set table with bogus data.
+    */
+    case SRT_Set: {
+      int lbl = sqliteVdbeMakeLabel(v);
+      assert( nColumn==1 );
+      sqliteVdbeAddOp(v, OP_IsNull, -1, lbl);
+      if( pOrderBy ){
+        pushOntoSorter(pParse, v, pOrderBy);
+      }else{
+        sqliteVdbeAddOp(v, OP_String, 0, 0);
+        sqliteVdbeAddOp(v, OP_PutStrKey, iParm, 0);
+      }
+      sqliteVdbeResolveLabel(v, lbl);
+      break;
+    }
+
+    /* If this is a scalar select that is part of an expression, then
+    ** store the results in the appropriate memory cell and break out
+    ** of the scan loop.
+    */
+    case SRT_Mem: {
+      assert( nColumn==1 );
+      if( pOrderBy ){
+        pushOntoSorter(pParse, v, pOrderBy);
+      }else{
+        sqliteVdbeAddOp(v, OP_MemStore, iParm, 1);
+        sqliteVdbeAddOp(v, OP_Goto, 0, iBreak);
+      }
+      break;
+    }
+
+    /* Send the data to the callback function.
+    */
+    case SRT_Callback:
+    case SRT_Sorter: {
+      if( pOrderBy ){
+        sqliteVdbeAddOp(v, OP_SortMakeRec, nColumn, 0);
+        pushOntoSorter(pParse, v, pOrderBy);
+      }else{
+        assert( eDest==SRT_Callback );
+        sqliteVdbeAddOp(v, OP_Callback, nColumn, 0);
+      }
+      break;
+    }
+
+    /* Invoke a subroutine to handle the results.  The subroutine itself
+    ** is responsible for popping the results off of the stack.
+    */
+    case SRT_Subroutine: {
+      if( pOrderBy ){
+        sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, 0);
+        pushOntoSorter(pParse, v, pOrderBy);
+      }else{
+        sqliteVdbeAddOp(v, OP_Gosub, 0, iParm);
+      }
+      break;
+    }
+
+    /* Discard the results.  This is used for SELECT statements inside
+    ** the body of a TRIGGER.  The purpose of such selects is to call
+    ** user-defined functions that have side effects.  We do not care
+    ** about the actual results of the select.
+    */
+    default: {
+      assert( eDest==SRT_Discard );
+      sqliteVdbeAddOp(v, OP_Pop, nColumn, 0);
+      break;
+    }
+  }
+  return 0;
+}
+
+/*
+** If the inner loop was generated using a non-null pOrderBy argument,
+** then the results were placed in a sorter.  After the loop is terminated
+** we need to run the sorter and output the results.  The following
+** routine generates the code needed to do that.
+*/
+static void generateSortTail(
+  Select *p,       /* The SELECT statement */
+  Vdbe *v,         /* Generate code into this VDBE */
+  int nColumn,     /* Number of columns of data */
+  int eDest,       /* Write the sorted results here */
+  int iParm        /* Optional parameter associated with eDest */
+){
+  int end = sqliteVdbeMakeLabel(v);
+  int addr;
+  if( eDest==SRT_Sorter ) return;
+  sqliteVdbeAddOp(v, OP_Sort, 0, 0);
+  addr = sqliteVdbeAddOp(v, OP_SortNext, 0, end);
+  if( p->nOffset>0 ){
+    sqliteVdbeAddOp(v, OP_MemIncr, p->nOffset, addr+4);
+    sqliteVdbeAddOp(v, OP_Pop, 1, 0);
+    sqliteVdbeAddOp(v, OP_Goto, 0, addr);
+  }
+  if( p->nLimit>=0 ){
+    sqliteVdbeAddOp(v, OP_MemIncr, p->nLimit, end);
+  }
+  switch( eDest ){
+    case SRT_Callback: {
+      sqliteVdbeAddOp(v, OP_SortCallback, nColumn, 0);
+      break;
+    }
+    case SRT_Table:
+    case SRT_TempTable: {
+      sqliteVdbeAddOp(v, OP_NewRecno, iParm, 0);
+      sqliteVdbeAddOp(v, OP_Pull, 1, 0);
+      sqliteVdbeAddOp(v, OP_PutIntKey, iParm, 0);
+      break;
+    }
+    case SRT_Set: {
+      assert( nColumn==1 );
+      sqliteVdbeAddOp(v, OP_IsNull, -1, sqliteVdbeCurrentAddr(v)+3);
+      sqliteVdbeAddOp(v, OP_String, 0, 0);
+      sqliteVdbeAddOp(v, OP_PutStrKey, iParm, 0);
+      break;
+    }
+    case SRT_Mem: {
+      assert( nColumn==1 );
+      sqliteVdbeAddOp(v, OP_MemStore, iParm, 1);
+      sqliteVdbeAddOp(v, OP_Goto, 0, end);
+      break;
+    }
+    case SRT_Subroutine: {
+      int i;
+      for(i=0; i<nColumn; i++){
+        sqliteVdbeAddOp(v, OP_Column, -1-i, i);
+      }
+      sqliteVdbeAddOp(v, OP_Gosub, 0, iParm);
+      sqliteVdbeAddOp(v, OP_Pop, 1, 0);
+      break;
+    }
+    default: {
+      /* Do nothing */
+      break;
+    }
+  }
+  sqliteVdbeAddOp(v, OP_Goto, 0, addr);
+  sqliteVdbeResolveLabel(v, end);
+  sqliteVdbeAddOp(v, OP_SortReset, 0, 0);
+}
+
+/*
+** Generate code that will tell the VDBE the datatypes of
+** columns in the result set.
+**
+** This routine only generates code if the "PRAGMA show_datatypes=on"
+** has been executed.  The datatypes are reported out in the azCol
+** parameter to the callback function.  The first N azCol[] entries
+** are the names of the columns, and the second N entries are the
+** datatypes for the columns.
+**
+** The "datatype" for a result that is a column of a type is the
+** datatype definition extracted from the CREATE TABLE statement.
+** The datatype for an expression is either TEXT or NUMERIC.  The
+** datatype for a ROWID field is INTEGER.
+*/
+static void generateColumnTypes(
+  Parse *pParse,      /* Parser context */
+  int base,           /* VDBE cursor corresponding to first entry in pTabList */
+  SrcList *pTabList,  /* List of tables */
+  ExprList *pEList    /* Expressions defining the result set */
+){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  if( pParse->useCallback && (pParse->db->flags & SQLITE_ReportTypes)==0 ){
+    return;
+  }
+  for(i=0; i<pEList->nExpr; i++){
+    Expr *p = pEList->a[i].pExpr;
+    char *zType = 0;
+    if( p==0 ) continue;
+    if( p->op==TK_COLUMN && pTabList ){
+      Table *pTab = pTabList->a[p->iTable - base].pTab;
+      int iCol = p->iColumn;
+      if( iCol<0 ) iCol = pTab->iPKey;
+      assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
+      if( iCol<0 ){
+        zType = "INTEGER";
+      }else{
+        zType = pTab->aCol[iCol].zType;
+      }
+    }else{
+      if( sqliteExprType(p)==SQLITE_SO_TEXT ){
+        zType = "TEXT";
+      }else{
+        zType = "NUMERIC";
+      }
+    }
+    sqliteVdbeAddOp(v, OP_ColumnName, i + pEList->nExpr, 0);
+    sqliteVdbeChangeP3(v, -1, zType, P3_STATIC);
+  }
+}
+
+/*
+** Generate code that will tell the VDBE the names of columns
+** in the result set.  This information is used to provide the
+** azCol[] vaolues in the callback.
+*/
+static void generateColumnNames(
+  Parse *pParse,      /* Parser context */
+  int base,           /* VDBE cursor corresponding to first entry in pTabList */
+  SrcList *pTabList,  /* List of tables */
+  ExprList *pEList    /* Expressions defining the result set */
+){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  if( pParse->colNamesSet || v==0 || sqlite_malloc_failed ) return;
+  pParse->colNamesSet = 1;
+  for(i=0; i<pEList->nExpr; i++){
+    Expr *p;
+    char *zType = 0;
+    int showFullNames;
+    p = pEList->a[i].pExpr;
+    if( p==0 ) continue;
+    if( pEList->a[i].zName ){
+      char *zName = pEList->a[i].zName;
+      sqliteVdbeAddOp(v, OP_ColumnName, i, 0);
+      sqliteVdbeChangeP3(v, -1, zName, strlen(zName));
+      continue;
+    }
+    showFullNames = (pParse->db->flags & SQLITE_FullColNames)!=0;
+    if( p->op==TK_COLUMN && pTabList ){
+      Table *pTab = pTabList->a[p->iTable - base].pTab;
+      char *zCol;
+      int iCol = p->iColumn;
+      if( iCol<0 ) iCol = pTab->iPKey;
+      assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
+      if( iCol<0 ){
+        zCol = "_ROWID_";
+        zType = "INTEGER";
+      }else{
+        zCol = pTab->aCol[iCol].zName;
+        zType = pTab->aCol[iCol].zType;
+      }
+      if( p->span.z && p->span.z[0] && !showFullNames ){
+        int addr = sqliteVdbeAddOp(v,OP_ColumnName, i, 0);
+        sqliteVdbeChangeP3(v, -1, p->span.z, p->span.n);
+        sqliteVdbeCompressSpace(v, addr);
+      }else if( pTabList->nSrc>1 || showFullNames ){
+        char *zName = 0;
+        char *zTab;
+ 
+        zTab = pTabList->a[p->iTable - base].zAlias;
+        if( showFullNames || zTab==0 ) zTab = pTab->zName;
+        sqliteSetString(&zName, zTab, ".", zCol, 0);
+        sqliteVdbeAddOp(v, OP_ColumnName, i, 0);
+        sqliteVdbeChangeP3(v, -1, zName, strlen(zName));
+        sqliteFree(zName);
+      }else{
+        sqliteVdbeAddOp(v, OP_ColumnName, i, 0);
+        sqliteVdbeChangeP3(v, -1, zCol, 0);
+      }
+    }else if( p->span.z && p->span.z[0] ){
+      int addr = sqliteVdbeAddOp(v,OP_ColumnName, i, 0);
+      sqliteVdbeChangeP3(v, -1, p->span.z, p->span.n);
+      sqliteVdbeCompressSpace(v, addr);
+    }else{
+      char zName[30];
+      assert( p->op!=TK_COLUMN || pTabList==0 );
+      sprintf(zName, "column%d", i+1);
+      sqliteVdbeAddOp(v, OP_ColumnName, i, 0);
+      sqliteVdbeChangeP3(v, -1, zName, strlen(zName));
+    }
+  }
+}
+
+/*
+** Name of the connection operator, used for error messages.
+*/
+static const char *selectOpName(int id){
+  char *z;
+  switch( id ){
+    case TK_ALL:       z = "UNION ALL";   break;
+    case TK_INTERSECT: z = "INTERSECT";   break;
+    case TK_EXCEPT:    z = "EXCEPT";      break;
+    default:           z = "UNION";       break;
+  }
+  return z;
+}
+
+/*
+** Forward declaration
+*/
+static int fillInColumnList(Parse*, Select*);
+
+/*
+** Given a SELECT statement, generate a Table structure that describes
+** the result set of that SELECT.
+*/
+Table *sqliteResultSetOfSelect(Parse *pParse, char *zTabName, Select *pSelect){
+  Table *pTab;
+  int i;
+  ExprList *pEList;
+
+  if( fillInColumnList(pParse, pSelect) ){
+    return 0;
+  }
+  pTab = sqliteMalloc( sizeof(Table) );
+  if( pTab==0 ){
+    return 0;
+  }
+  pTab->zName = zTabName ? sqliteStrDup(zTabName) : 0;
+  pEList = pSelect->pEList;
+  pTab->nCol = pEList->nExpr;
+  assert( pTab->nCol>0 );
+  pTab->aCol = sqliteMalloc( sizeof(pTab->aCol[0])*pTab->nCol );
+  for(i=0; i<pTab->nCol; i++){
+    Expr *p;
+    if( pEList->a[i].zName ){
+      pTab->aCol[i].zName = sqliteStrDup(pEList->a[i].zName);
+    }else if( (p=pEList->a[i].pExpr)->span.z && p->span.z[0] ){
+      sqliteSetNString(&pTab->aCol[i].zName, p->span.z, p->span.n, 0);
+    }else if( p->op==TK_DOT && p->pRight && p->pRight->token.z &&
+           p->pRight->token.z[0] ){
+      sqliteSetNString(&pTab->aCol[i].zName, 
+           p->pRight->token.z, p->pRight->token.n, 0);
+    }else{
+      char zBuf[30];
+      sprintf(zBuf, "column%d", i+1);
+      pTab->aCol[i].zName = sqliteStrDup(zBuf);
+    }
+  }
+  pTab->iPKey = -1;
+  return pTab;
+}
+
+/*
+** For the given SELECT statement, do three things.
+**
+**    (1)  Fill in the pTabList->a[].pTab fields in the SrcList that 
+**         defines the set of tables that should be scanned. 
+**
+**    (2)  Add terms to the WHERE clause to accomodate the NATURAL keyword
+**         on joins and the ON and USING clause of joins.
+**
+**    (3)  Scan the list of columns in the result set (pEList) looking
+**         for instances of the "*" operator or the TABLE.* operator.
+**         If found, expand each "*" to be every column in every table
+**         and TABLE.* to be every column in TABLE.
+**
+** Return 0 on success.  If there are problems, leave an error message
+** in pParse and return non-zero.
+*/
+static int fillInColumnList(Parse *pParse, Select *p){
+  int i, j, k, rc;
+  SrcList *pTabList;
+  ExprList *pEList;
+  Table *pTab;
+
+  if( p==0 || p->pSrc==0 ) return 1;
+  pTabList = p->pSrc;
+  pEList = p->pEList;
+
+  /* Look up every table in the table list.
+  */
+  for(i=0; i<pTabList->nSrc; i++){
+    if( pTabList->a[i].pTab ){
+      /* This routine has run before!  No need to continue */
+      return 0;
+    }
+    if( pTabList->a[i].zName==0 ){
+      /* A sub-query in the FROM clause of a SELECT */
+      assert( pTabList->a[i].pSelect!=0 );
+      if( pTabList->a[i].zAlias==0 ){
+        char zFakeName[60];
+        sprintf(zFakeName, "sqlite_subquery_%p_",
+           (void*)pTabList->a[i].pSelect);
+        sqliteSetString(&pTabList->a[i].zAlias, zFakeName, 0);
+      }
+      pTabList->a[i].pTab = pTab = 
+        sqliteResultSetOfSelect(pParse, pTabList->a[i].zAlias,
+                                        pTabList->a[i].pSelect);
+      if( pTab==0 ){
+        return 1;
+      }
+      pTab->isTransient = 1;
+    }else{
+      /* An ordinary table or view name in the FROM clause */
+      pTabList->a[i].pTab = pTab = 
+        sqliteFindTable(pParse->db, pTabList->a[i].zName);
+      if( pTab==0 ){
+        sqliteSetString(&pParse->zErrMsg, "no such table: ", 
+           pTabList->a[i].zName, 0);
+        pParse->nErr++;
+        return 1;
+      }
+      if( pTab->pSelect ){
+        if( sqliteViewGetColumnNames(pParse, pTab) ){
+          return 1;
+        }
+        sqliteSelectDelete(pTabList->a[i].pSelect);
+        pTabList->a[i].pSelect = sqliteSelectDup(pTab->pSelect);
+      }
+    }
+  }
+
+  /* Process NATURAL keywords, and ON and USING clauses of joins.
+  */
+  if( sqliteProcessJoin(pParse, p) ) return 1;
+
+  /* For every "*" that occurs in the column list, insert the names of
+  ** all columns in all tables.  And for every TABLE.* insert the names
+  ** of all columns in TABLE.  The parser inserted a special expression
+  ** with the TK_ALL operator for each "*" that it found in the column list.
+  ** The following code just has to locate the TK_ALL expressions and expand
+  ** each one to the list of all columns in all tables.
+  **
+  ** The first loop just checks to see if there are any "*" operators
+  ** that need expanding.
+  */
+  for(k=0; k<pEList->nExpr; k++){
+    Expr *pE = pEList->a[k].pExpr;
+    if( pE->op==TK_ALL ) break;
+    if( pE->op==TK_DOT && pE->pRight && pE->pRight->op==TK_ALL
+         && pE->pLeft && pE->pLeft->op==TK_ID ) break;
+  }
+  rc = 0;
+  if( k<pEList->nExpr ){
+    /*
+    ** If we get here it means the result set contains one or more "*"
+    ** operators that need to be expanded.  Loop through each expression
+    ** in the result set and expand them one by one.
+    */
+    struct ExprList_item *a = pEList->a;
+    ExprList *pNew = 0;
+    for(k=0; k<pEList->nExpr; k++){
+      Expr *pE = a[k].pExpr;
+      if( pE->op!=TK_ALL &&
+           (pE->op!=TK_DOT || pE->pRight==0 || pE->pRight->op!=TK_ALL) ){
+        /* This particular expression does not need to be expanded.
+        */
+        pNew = sqliteExprListAppend(pNew, a[k].pExpr, 0);
+        pNew->a[pNew->nExpr-1].zName = a[k].zName;
+        a[k].pExpr = 0;
+        a[k].zName = 0;
+      }else{
+        /* This expression is a "*" or a "TABLE.*" and needs to be
+        ** expanded. */
+        int tableSeen = 0;      /* Set to 1 when TABLE matches */
+        Token *pName;           /* text of name of TABLE */
+        if( pE->op==TK_DOT && pE->pLeft ){
+          pName = &pE->pLeft->token;
+        }else{
+          pName = 0;
+        }
+        for(i=0; i<pTabList->nSrc; i++){
+          Table *pTab = pTabList->a[i].pTab;
+          char *zTabName = pTabList->a[i].zAlias;
+          if( zTabName==0 || zTabName[0]==0 ){ 
+            zTabName = pTab->zName;
+          }
+          if( pName && (zTabName==0 || zTabName[0]==0 || 
+                 sqliteStrNICmp(pName->z, zTabName, pName->n)!=0 ||
+                 zTabName[pName->n]!=0) ){
+            continue;
+          }
+          tableSeen = 1;
+          for(j=0; j<pTab->nCol; j++){
+            Expr *pExpr, *pLeft, *pRight;
+            char *zName = pTab->aCol[j].zName;
+
+            if( i>0 && (pTabList->a[i-1].jointype & JT_NATURAL)!=0 &&
+                columnIndex(pTabList->a[i-1].pTab, zName)>=0 ){
+              /* In a NATURAL join, omit the join columns from the 
+              ** table on the right */
+              continue;
+            }
+            if( i>0 && sqliteIdListIndex(pTabList->a[i-1].pUsing, zName)>=0 ){
+              /* In a join with a USING clause, omit columns in the
+              ** using clause from the table on the right. */
+              continue;
+            }
+            pRight = sqliteExpr(TK_ID, 0, 0, 0);
+            if( pRight==0 ) break;
+            pRight->token.z = zName;
+            pRight->token.n = strlen(zName);
+            pRight->token.dyn = 0;
+            if( zTabName && pTabList->nSrc>1 ){
+              pLeft = sqliteExpr(TK_ID, 0, 0, 0);
+              pExpr = sqliteExpr(TK_DOT, pLeft, pRight, 0);
+              if( pExpr==0 ) break;
+              pLeft->token.z = zTabName;
+              pLeft->token.n = strlen(zTabName);
+              pLeft->token.dyn = 0;
+              sqliteSetString((char**)&pExpr->span.z, zTabName, ".", zName, 0);
+              pExpr->span.n = strlen(pExpr->span.z);
+              pExpr->span.dyn = 1;
+              pExpr->token.z = 0;
+              pExpr->token.n = 0;
+              pExpr->token.dyn = 0;
+            }else{
+              pExpr = pRight;
+              pExpr->span = pExpr->token;
+            }
+            pNew = sqliteExprListAppend(pNew, pExpr, 0);
+          }
+        }
+        if( !tableSeen ){
+          if( pName ){
+            sqliteSetNString(&pParse->zErrMsg, "no such table: ", -1, 
+              pName->z, pName->n, 0);
+          }else{
+            sqliteSetString(&pParse->zErrMsg, "no tables specified", 0);
+          }
+          rc = 1;
+        }
+      }
+    }
+    sqliteExprListDelete(pEList);
+    p->pEList = pNew;
+  }
+  return rc;
+}
+
+/*
+** This routine recursively unlinks the Select.pSrc.a[].pTab pointers
+** in a select structure.  It just sets the pointers to NULL.  This
+** routine is recursive in the sense that if the Select.pSrc.a[].pSelect
+** pointer is not NULL, this routine is called recursively on that pointer.
+**
+** This routine is called on the Select structure that defines a
+** VIEW in order to undo any bindings to tables.  This is necessary
+** because those tables might be DROPed by a subsequent SQL command.
+*/
+void sqliteSelectUnbind(Select *p){
+  int i;
+  SrcList *pSrc = p->pSrc;
+  Table *pTab;
+  if( p==0 ) return;
+  for(i=0; i<pSrc->nSrc; i++){
+    if( (pTab = pSrc->a[i].pTab)!=0 ){
+      if( pTab->isTransient ){
+        sqliteDeleteTable(0, pTab);
+#if 0
+        sqliteSelectDelete(pSrc->a[i].pSelect);
+        pSrc->a[i].pSelect = 0;
+#endif
+      }
+      pSrc->a[i].pTab = 0;
+      if( pSrc->a[i].pSelect ){
+        sqliteSelectUnbind(pSrc->a[i].pSelect);
+      }
+    }
+  }
+}
+
+/*
+** This routine associates entries in an ORDER BY expression list with
+** columns in a result.  For each ORDER BY expression, the opcode of
+** the top-level node is changed to TK_COLUMN and the iColumn value of
+** the top-level node is filled in with column number and the iTable
+** value of the top-level node is filled with iTable parameter.
+**
+** If there are prior SELECT clauses, they are processed first.  A match
+** in an earlier SELECT takes precedence over a later SELECT.
+**
+** Any entry that does not match is flagged as an error.  The number
+** of errors is returned.
+**
+** This routine does NOT correctly initialize the Expr.dataType  field
+** of the ORDER BY expressions.  The multiSelectSortOrder() routine
+** must be called to do that after the individual select statements
+** have all been analyzed.  This routine is unable to compute Expr.dataType
+** because it must be called before the individual select statements
+** have been analyzed.
+*/
+static int matchOrderbyToColumn(
+  Parse *pParse,          /* A place to leave error messages */
+  Select *pSelect,        /* Match to result columns of this SELECT */
+  ExprList *pOrderBy,     /* The ORDER BY values to match against columns */
+  int iTable,             /* Insert this value in iTable */
+  int mustComplete        /* If TRUE all ORDER BYs must match */
+){
+  int nErr = 0;
+  int i, j;
+  ExprList *pEList;
+
+  if( pSelect==0 || pOrderBy==0 ) return 1;
+  if( mustComplete ){
+    for(i=0; i<pOrderBy->nExpr; i++){ pOrderBy->a[i].done = 0; }
+  }
+  if( fillInColumnList(pParse, pSelect) ){
+    return 1;
+  }
+  if( pSelect->pPrior ){
+    if( matchOrderbyToColumn(pParse, pSelect->pPrior, pOrderBy, iTable, 0) ){
+      return 1;
+    }
+  }
+  pEList = pSelect->pEList;
+  for(i=0; i<pOrderBy->nExpr; i++){
+    Expr *pE = pOrderBy->a[i].pExpr;
+    int iCol = -1;
+    if( pOrderBy->a[i].done ) continue;
+    if( sqliteExprIsInteger(pE, &iCol) ){
+      if( iCol<=0 || iCol>pEList->nExpr ){
+        char zBuf[200];
+        sprintf(zBuf,"ORDER BY position %d should be between 1 and %d",
+           iCol, pEList->nExpr);
+        sqliteSetString(&pParse->zErrMsg, zBuf, 0);
+        pParse->nErr++;
+        nErr++;
+        break;
+      }
+      if( !mustComplete ) continue;
+      iCol--;
+    }
+    for(j=0; iCol<0 && j<pEList->nExpr; j++){
+      if( pEList->a[j].zName && (pE->op==TK_ID || pE->op==TK_STRING) ){
+        char *zName, *zLabel;
+        zName = pEList->a[j].zName;
+        assert( pE->token.z );
+        zLabel = sqliteStrNDup(pE->token.z, pE->token.n);
+        sqliteDequote(zLabel);
+        if( sqliteStrICmp(zName, zLabel)==0 ){ 
+          iCol = j;
+        }
+        sqliteFree(zLabel);
+      }
+      if( iCol<0 && sqliteExprCompare(pE, pEList->a[j].pExpr) ){
+        iCol = j;
+      }
+    }
+    if( iCol>=0 ){
+      pE->op = TK_COLUMN;
+      pE->iColumn = iCol;
+      pE->iTable = iTable;
+      pOrderBy->a[i].done = 1;
+    }
+    if( iCol<0 && mustComplete ){
+      char zBuf[30];
+      sprintf(zBuf,"%d",i+1);
+      sqliteSetString(&pParse->zErrMsg, "ORDER BY term number ", zBuf, 
+        " does not match any result column", 0);
+      pParse->nErr++;
+      nErr++;
+      break;
+    }
+  }
+  return nErr;  
+}
+
+/*
+** Get a VDBE for the given parser context.  Create a new one if necessary.
+** If an error occurs, return NULL and leave a message in pParse.
+*/
+Vdbe *sqliteGetVdbe(Parse *pParse){
+  Vdbe *v = pParse->pVdbe;
+  if( v==0 ){
+    v = pParse->pVdbe = sqliteVdbeCreate(pParse->db);
+  }
+  return v;
+}
+
+/*
+** This routine sets the Expr.dataType field on all elements of
+** the pOrderBy expression list.  The pOrderBy list will have been
+** set up by matchOrderbyToColumn().  Hence each expression has
+** a TK_COLUMN as its root node.  The Expr.iColumn refers to a 
+** column in the result set.   The datatype is set to SQLITE_SO_TEXT
+** if the corresponding column in p and every SELECT to the left of
+** p has a datatype of SQLITE_SO_TEXT.  If the cooressponding column
+** in p or any of the left SELECTs is SQLITE_SO_NUM, then the datatype
+** of the order-by expression is set to SQLITE_SO_NUM.
+**
+** Examples:
+**
+**     CREATE TABLE one(a INTEGER, b TEXT);
+**     CREATE TABLE two(c VARCHAR(5), d FLOAT);
+**
+**     SELECT b, b FROM one UNION SELECT d, c FROM two ORDER BY 1, 2;
+**
+** The primary sort key will use SQLITE_SO_NUM because the "d" in
+** the second SELECT is numeric.  The 1st column of the first SELECT
+** is text but that does not matter because a numeric always overrides
+** a text.
+**
+** The secondary key will use the SQLITE_SO_TEXT sort order because
+** both the (second) "b" in the first SELECT and the "c" in the second
+** SELECT have a datatype of text.
+*/ 
+static void multiSelectSortOrder(Select *p, ExprList *pOrderBy){
+  int i;
+  ExprList *pEList;
+  if( pOrderBy==0 ) return;
+  if( p==0 ){
+    for(i=0; i<pOrderBy->nExpr; i++){
+      pOrderBy->a[i].pExpr->dataType = SQLITE_SO_TEXT;
+    }
+    return;
+  }
+  multiSelectSortOrder(p->pPrior, pOrderBy);
+  pEList = p->pEList;
+  for(i=0; i<pOrderBy->nExpr; i++){
+    Expr *pE = pOrderBy->a[i].pExpr;
+    if( pE->dataType==SQLITE_SO_NUM ) continue;
+    assert( pE->iColumn>=0 );
+    if( pEList->nExpr>pE->iColumn ){
+      pE->dataType = sqliteExprType(pEList->a[pE->iColumn].pExpr);
+    }
+  }
+}
+
+/*
+** This routine is called to process a query that is really the union
+** or intersection of two or more separate queries.
+**
+** "p" points to the right-most of the two queries.  the query on the
+** left is p->pPrior.  The left query could also be a compound query
+** in which case this routine will be called recursively. 
+**
+** The results of the total query are to be written into a destination
+** of type eDest with parameter iParm.
+**
+** Example 1:  Consider a three-way compound SQL statement.
+**
+**     SELECT a FROM t1 UNION SELECT b FROM t2 UNION SELECT c FROM t3
+**
+** This statement is parsed up as follows:
+**
+**     SELECT c FROM t3
+**      |
+**      `----->  SELECT b FROM t2
+**                |
+**                `------>  SELECT c FROM t1
+**
+** The arrows in the diagram above represent the Select.pPrior pointer.
+** So if this routine is called with p equal to the t3 query, then
+** pPrior will be the t2 query.  p->op will be TK_UNION in this case.
+**
+** Notice that because of the way SQLite parses compound SELECTs, the
+** individual selects always group from left to right.
+*/
+static int multiSelect(Parse *pParse, Select *p, int eDest, int iParm){
+  int rc;             /* Success code from a subroutine */
+  Select *pPrior;     /* Another SELECT immediately to our left */
+  Vdbe *v;            /* Generate code to this VDBE */
+
+  /* Make sure there is no ORDER BY clause on prior SELECTs.  Only the 
+  ** last SELECT in the series may have an ORDER BY.
+  */
+  if( p==0 || p->pPrior==0 ) return 1;
+  pPrior = p->pPrior;
+  if( pPrior->pOrderBy ){
+    sqliteSetString(&pParse->zErrMsg,"ORDER BY clause should come after ",
+      selectOpName(p->op), " not before", 0);
+    pParse->nErr++;
+    return 1;
+  }
+
+  /* Make sure we have a valid query engine.  If not, create a new one.
+  */
+  v = sqliteGetVdbe(pParse);
+  if( v==0 ) return 1;
+
+  /* Create the destination temporary table if necessary
+  */
+  if( eDest==SRT_TempTable ){
+    sqliteVdbeAddOp(v, OP_OpenTemp, iParm, 0);
+    eDest = SRT_Table;
+  }
+
+  /* Generate code for the left and right SELECT statements.
+  */
+  switch( p->op ){
+    case TK_ALL: {
+      if( p->pOrderBy==0 ){
+        rc = sqliteSelect(pParse, pPrior, eDest, iParm, 0, 0, 0);
+        if( rc ) return rc;
+        p->pPrior = 0;
+        rc = sqliteSelect(pParse, p, eDest, iParm, 0, 0, 0);
+        p->pPrior = pPrior;
+        if( rc ) return rc;
+        break;
+      }
+      /* For UNION ALL ... ORDER BY fall through to the next case */
+    }
+    case TK_EXCEPT:
+    case TK_UNION: {
+      int unionTab;    /* Cursor number of the temporary table holding result */
+      int op;          /* One of the SRT_ operations to apply to self */
+      int priorOp;     /* The SRT_ operation to apply to prior selects */
+      ExprList *pOrderBy;  /* The ORDER BY clause for the right SELECT */
+
+      priorOp = p->op==TK_ALL ? SRT_Table : SRT_Union;
+      if( eDest==priorOp && p->pOrderBy==0 ){
+        /* We can reuse a temporary table generated by a SELECT to our
+        ** right.
+        */
+        unionTab = iParm;
+      }else{
+        /* We will need to create our own temporary table to hold the
+        ** intermediate results.
+        */
+        unionTab = pParse->nTab++;
+        if( p->pOrderBy 
+        && matchOrderbyToColumn(pParse, p, p->pOrderBy, unionTab, 1) ){
+          return 1;
+        }
+        if( p->op!=TK_ALL ){
+          sqliteVdbeAddOp(v, OP_OpenTemp, unionTab, 1);
+          sqliteVdbeAddOp(v, OP_KeyAsData, unionTab, 1);
+        }else{
+          sqliteVdbeAddOp(v, OP_OpenTemp, unionTab, 0);
+        }
+      }
+
+      /* Code the SELECT statements to our left
+      */
+      rc = sqliteSelect(pParse, pPrior, priorOp, unionTab, 0, 0, 0);
+      if( rc ) return rc;
+
+      /* Code the current SELECT statement
+      */
+      switch( p->op ){
+         case TK_EXCEPT:  op = SRT_Except;   break;
+         case TK_UNION:   op = SRT_Union;    break;
+         case TK_ALL:     op = SRT_Table;    break;
+      }
+      p->pPrior = 0;
+      pOrderBy = p->pOrderBy;
+      p->pOrderBy = 0;
+      rc = sqliteSelect(pParse, p, op, unionTab, 0, 0, 0);
+      p->pPrior = pPrior;
+      p->pOrderBy = pOrderBy;
+      if( rc ) return rc;
+
+      /* Convert the data in the temporary table into whatever form
+      ** it is that we currently need.
+      */      
+      if( eDest!=priorOp || unionTab!=iParm ){
+        int iCont, iBreak, iStart;
+        assert( p->pEList );
+        if( eDest==SRT_Callback ){
+          generateColumnNames(pParse, p->base, 0, p->pEList);
+          generateColumnTypes(pParse, p->base, p->pSrc, p->pEList);
+        }
+        iBreak = sqliteVdbeMakeLabel(v);
+        iCont = sqliteVdbeMakeLabel(v);
+        sqliteVdbeAddOp(v, OP_Rewind, unionTab, iBreak);
+        iStart = sqliteVdbeCurrentAddr(v);
+        multiSelectSortOrder(p, p->pOrderBy);
+        rc = selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
+                             p->pOrderBy, -1, eDest, iParm, 
+                             iCont, iBreak);
+        if( rc ) return 1;
+        sqliteVdbeResolveLabel(v, iCont);
+        sqliteVdbeAddOp(v, OP_Next, unionTab, iStart);
+        sqliteVdbeResolveLabel(v, iBreak);
+        sqliteVdbeAddOp(v, OP_Close, unionTab, 0);
+        if( p->pOrderBy ){
+          generateSortTail(p, v, p->pEList->nExpr, eDest, iParm);
+        }
+      }
+      break;
+    }
+    case TK_INTERSECT: {
+      int tab1, tab2;
+      int iCont, iBreak, iStart;
+
+      /* INTERSECT is different from the others since it requires
+      ** two temporary tables.  Hence it has its own case.  Begin
+      ** by allocating the tables we will need.
+      */
+      tab1 = pParse->nTab++;
+      tab2 = pParse->nTab++;
+      if( p->pOrderBy && matchOrderbyToColumn(pParse,p,p->pOrderBy,tab1,1) ){
+        return 1;
+      }
+      sqliteVdbeAddOp(v, OP_OpenTemp, tab1, 1);
+      sqliteVdbeAddOp(v, OP_KeyAsData, tab1, 1);
+
+      /* Code the SELECTs to our left into temporary table "tab1".
+      */
+      rc = sqliteSelect(pParse, pPrior, SRT_Union, tab1, 0, 0, 0);
+      if( rc ) return rc;
+
+      /* Code the current SELECT into temporary table "tab2"
+      */
+      sqliteVdbeAddOp(v, OP_OpenTemp, tab2, 1);
+      sqliteVdbeAddOp(v, OP_KeyAsData, tab2, 1);
+      p->pPrior = 0;
+      rc = sqliteSelect(pParse, p, SRT_Union, tab2, 0, 0, 0);
+      p->pPrior = pPrior;
+      if( rc ) return rc;
+
+      /* Generate code to take the intersection of the two temporary
+      ** tables.
+      */
+      assert( p->pEList );
+      if( eDest==SRT_Callback ){
+        generateColumnNames(pParse, p->base, 0, p->pEList);
+        generateColumnTypes(pParse, p->base, p->pSrc, p->pEList);
+      }
+      iBreak = sqliteVdbeMakeLabel(v);
+      iCont = sqliteVdbeMakeLabel(v);
+      sqliteVdbeAddOp(v, OP_Rewind, tab1, iBreak);
+      iStart = sqliteVdbeAddOp(v, OP_FullKey, tab1, 0);
+      sqliteVdbeAddOp(v, OP_NotFound, tab2, iCont);
+      multiSelectSortOrder(p, p->pOrderBy);
+      rc = selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
+                             p->pOrderBy, -1, eDest, iParm, 
+                             iCont, iBreak);
+      if( rc ) return 1;
+      sqliteVdbeResolveLabel(v, iCont);
+      sqliteVdbeAddOp(v, OP_Next, tab1, iStart);
+      sqliteVdbeResolveLabel(v, iBreak);
+      sqliteVdbeAddOp(v, OP_Close, tab2, 0);
+      sqliteVdbeAddOp(v, OP_Close, tab1, 0);
+      if( p->pOrderBy ){
+        generateSortTail(p, v, p->pEList->nExpr, eDest, iParm);
+      }
+      break;
+    }
+  }
+  assert( p->pEList && pPrior->pEList );
+  if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
+    sqliteSetString(&pParse->zErrMsg, "SELECTs to the left and right of ",
+      selectOpName(p->op), " do not have the same number of result columns", 0);
+    pParse->nErr++;
+    return 1;
+  }
+
+  /* Issue a null callback if that is what the user wants.
+  */
+  if( eDest==SRT_Callback &&
+    (pParse->useCallback==0 || (pParse->db->flags & SQLITE_NullCallback)!=0)
+  ){
+    sqliteVdbeAddOp(v, OP_NullCallback, p->pEList->nExpr, 0);
+  }
+  return 0;
+}
+
+/*
+** Recursively scan through an expression tree.  For every reference
+** to a column in table number iFrom, change that reference to the
+** same column in table number iTo.
+*/
+static void changeTablesInList(ExprList*, int, int);  /* Forward Declaration */
+static void changeTables(Expr *pExpr, int iFrom, int iTo){
+  if( pExpr==0 ) return;
+  if( pExpr->op==TK_COLUMN && pExpr->iTable==iFrom ){
+    pExpr->iTable = iTo;
+  }else{
+    changeTables(pExpr->pLeft, iFrom, iTo);
+    changeTables(pExpr->pRight, iFrom, iTo);
+    changeTablesInList(pExpr->pList, iFrom, iTo);
+  }
+}
+static void changeTablesInList(ExprList *pList, int iFrom, int iTo){
+  if( pList ){
+    int i;
+    for(i=0; i<pList->nExpr; i++){
+      changeTables(pList->a[i].pExpr, iFrom, iTo);
+    }
+  }
+}
+
+/*
+** Scan through the expression pExpr.  Replace every reference to
+** a column in table number iTable with a copy of the corresponding
+** entry in pEList.  (But leave references to the ROWID column 
+** unchanged.)  When making a copy of an expression in pEList, change
+** references to columns in table iSub into references to table iTable.
+**
+** This routine is part of the flattening procedure.  A subquery
+** whose result set is defined by pEList appears as entry in the
+** FROM clause of a SELECT such that the VDBE cursor assigned to that
+** FORM clause entry is iTable.  This routine make the necessary 
+** changes to pExpr so that it refers directly to the source table
+** of the subquery rather the result set of the subquery.
+*/
+static void substExprList(ExprList*,int,ExprList*,int);  /* Forward Decl */
+static void substExpr(Expr *pExpr, int iTable, ExprList *pEList, int iSub){
+  if( pExpr==0 ) return;
+  if( pExpr->op==TK_COLUMN && pExpr->iTable==iTable && pExpr->iColumn>=0 ){
+    Expr *pNew;
+    assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
+    assert( pExpr->pLeft==0 && pExpr->pRight==0 && pExpr->pList==0 );
+    pNew = pEList->a[pExpr->iColumn].pExpr;
+    assert( pNew!=0 );
+    pExpr->op = pNew->op;
+    pExpr->dataType = pNew->dataType;
+    assert( pExpr->pLeft==0 );
+    pExpr->pLeft = sqliteExprDup(pNew->pLeft);
+    assert( pExpr->pRight==0 );
+    pExpr->pRight = sqliteExprDup(pNew->pRight);
+    assert( pExpr->pList==0 );
+    pExpr->pList = sqliteExprListDup(pNew->pList);
+    pExpr->iTable = pNew->iTable;
+    pExpr->iColumn = pNew->iColumn;
+    pExpr->iAgg = pNew->iAgg;
+    sqliteTokenCopy(&pExpr->token, &pNew->token);
+    sqliteTokenCopy(&pExpr->span, &pNew->span);
+    if( iSub!=iTable ){
+      changeTables(pExpr, iSub, iTable);
+    }
+  }else{
+    substExpr(pExpr->pLeft, iTable, pEList, iSub);
+    substExpr(pExpr->pRight, iTable, pEList, iSub);
+    substExprList(pExpr->pList, iTable, pEList, iSub);
+  }
+}
+static void 
+substExprList(ExprList *pList, int iTable, ExprList *pEList, int iSub){
+  int i;
+  if( pList==0 ) return;
+  for(i=0; i<pList->nExpr; i++){
+    substExpr(pList->a[i].pExpr, iTable, pEList, iSub);
+  }
+}
+
+/*
+** This routine attempts to flatten subqueries in order to speed
+** execution.  It returns 1 if it makes changes and 0 if no flattening
+** occurs.
+**
+** To understand the concept of flattening, consider the following
+** query:
+**
+**     SELECT a FROM (SELECT x+y AS a FROM t1 WHERE z<100) WHERE a>5
+**
+** The default way of implementing this query is to execute the
+** subquery first and store the results in a temporary table, then
+** run the outer query on that temporary table.  This requires two
+** passes over the data.  Furthermore, because the temporary table
+** has no indices, the WHERE clause on the outer query cannot be
+** optimized.
+**
+** This routine attempts to rewrite queries such as the above into
+** a single flat select, like this:
+**
+**     SELECT x+y AS a FROM t1 WHERE z<100 AND a>5
+**
+** The code generated for this simpification gives the same result
+** but only has to scan the data once.  And because indices might 
+** exist on the table t1, a complete scan of the data might be
+** avoided.
+**
+** Flattening is only attempted if all of the following are true:
+**
+**   (1)  The subquery and the outer query do not both use aggregates.
+**
+**   (2)  The subquery is not an aggregate or the outer query is not a join.
+**
+**   (3)  The subquery is not a join.
+**
+**   (4)  The subquery is not DISTINCT or the outer query is not a join.
+**
+**   (5)  The subquery is not DISTINCT or the outer query does not use
+**        aggregates.
+**
+**   (6)  The subquery does not use aggregates or the outer query is not
+**        DISTINCT.
+**
+**   (7)  The subquery has a FROM clause.
+**
+**   (8)  The subquery does not use LIMIT or the outer query is not a join.
+**
+**   (9)  The subquery does not use LIMIT or the outer query does not use
+**        aggregates.
+**
+**  (10)  The subquery does not use aggregates or the outer query does not
+**        use LIMIT.
+**
+**  (11)  The subquery and the outer query do not both have ORDER BY clauses.
+**
+** In this routine, the "p" parameter is a pointer to the outer query.
+** The subquery is p->pSrc->a[iFrom].  isAgg is true if the outer query
+** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
+**
+** If flattening is not attempted, this routine is a no-op and return 0.
+** If flattening is attempted this routine returns 1.
+**
+** All of the expression analysis must occur on both the outer query and
+** the subquery before this routine runs.
+*/
+static int flattenSubquery(
+  Parse *pParse,       /* The parsing context */
+  Select *p,           /* The parent or outer SELECT statement */
+  int iFrom,           /* Index in p->pSrc->a[] of the inner subquery */
+  int isAgg,           /* True if outer SELECT uses aggregate functions */
+  int subqueryIsAgg    /* True if the subquery uses aggregate functions */
+){
+  Select *pSub;       /* The inner query or "subquery" */
+  SrcList *pSrc;      /* The FROM clause of the outer query */
+  SrcList *pSubSrc;   /* The FROM clause of the subquery */
+  ExprList *pList;    /* The result set of the outer query */
+  int i;
+  int iParent, iSub;
+  Expr *pWhere;
+
+  /* Check to see if flattening is permitted.  Return 0 if not.
+  */
+  if( p==0 ) return 0;
+  pSrc = p->pSrc;
+  assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
+  pSub = pSrc->a[iFrom].pSelect;
+  assert( pSub!=0 );
+  if( isAgg && subqueryIsAgg ) return 0;
+  if( subqueryIsAgg && pSrc->nSrc>1 ) return 0;
+  pSubSrc = pSub->pSrc;
+  assert( pSubSrc );
+  if( pSubSrc->nSrc!=1 ) return 0;
+  if( (pSub->isDistinct || pSub->nLimit>=0) &&  (pSrc->nSrc>1 || isAgg) ){
+     return 0;
+  }
+  if( (p->isDistinct || p->nLimit>=0) && subqueryIsAgg ) return 0;
+  if( p->pOrderBy && pSub->pOrderBy ) return 0;
+
+  /* If we reach this point, it means flattening is permitted for the
+  ** i-th entry of the FROM clause in the outer query.
+  */
+  iParent = p->base + iFrom;
+  iSub = pSub->base;
+  substExprList(p->pEList, iParent, pSub->pEList, iSub);
+  pList = p->pEList;
+  for(i=0; i<pList->nExpr; i++){
+    Expr *pExpr;
+    if( pList->a[i].zName==0 && (pExpr = pList->a[i].pExpr)->span.z!=0 ){
+      pList->a[i].zName = sqliteStrNDup(pExpr->span.z, pExpr->span.n);
+    }
+  }
+  if( isAgg ){
+    substExprList(p->pGroupBy, iParent, pSub->pEList, iSub);
+    substExpr(p->pHaving, iParent, pSub->pEList, iSub);
+  }
+  if( pSub->pOrderBy ){
+    assert( p->pOrderBy==0 );
+    p->pOrderBy = pSub->pOrderBy;
+    pSub->pOrderBy = 0;
+    changeTablesInList(p->pOrderBy, iSub, iParent);
+  }else if( p->pOrderBy ){
+    substExprList(p->pOrderBy, iParent, pSub->pEList, iSub);
+  }
+  if( pSub->pWhere ){
+    pWhere = sqliteExprDup(pSub->pWhere);
+    if( iParent!=iSub ){
+      changeTables(pWhere, iSub, iParent);
+    }
+  }else{
+    pWhere = 0;
+  }
+  if( subqueryIsAgg ){
+    assert( p->pHaving==0 );
+    p->pHaving = p->pWhere;
+    p->pWhere = pWhere;
+    substExpr(p->pHaving, iParent, pSub->pEList, iSub);
+    if( pSub->pHaving ){
+      Expr *pHaving = sqliteExprDup(pSub->pHaving);
+      if( iParent!=iSub ){
+        changeTables(pHaving, iSub, iParent);
+      }
+      if( p->pHaving ){
+        p->pHaving = sqliteExpr(TK_AND, p->pHaving, pHaving, 0);
+      }else{
+        p->pHaving = pHaving;
+      }
+    }
+    assert( p->pGroupBy==0 );
+    p->pGroupBy = sqliteExprListDup(pSub->pGroupBy);
+    if( iParent!=iSub ){
+      changeTablesInList(p->pGroupBy, iSub, iParent);
+    }
+  }else if( p->pWhere==0 ){
+    p->pWhere = pWhere;
+  }else{
+    substExpr(p->pWhere, iParent, pSub->pEList, iSub);
+    if( pWhere ){
+      p->pWhere = sqliteExpr(TK_AND, p->pWhere, pWhere, 0);
+    }
+  }
+  p->isDistinct = p->isDistinct || pSub->isDistinct;
+
+  if( pSub->nLimit>=0 ){
+    if( p->nLimit<0 ){
+      p->nLimit = pSub->nLimit;
+    }else if( p->nLimit+p->nOffset > pSub->nLimit+pSub->nOffset ){
+      p->nLimit = pSub->nLimit + pSub->nOffset - p->nOffset;
+    }
+  }
+  p->nOffset += pSub->nOffset;
+
+  /* If the subquery contains subqueries of its own, that were not
+  ** flattened, then code will have already been generated to put
+  ** the results of those sub-subqueries into VDBE cursors relative
+  ** to the subquery.  We must translate the cursor number into values
+  ** suitable for use by the outer query.
+  */
+  for(i=0; i<pSubSrc->nSrc; i++){
+    Vdbe *v;
+    if( pSubSrc->a[i].pSelect==0 ) continue;
+    v = sqliteGetVdbe(pParse);
+    sqliteVdbeAddOp(v, OP_RenameCursor, pSub->base+i, p->base+i);
+  }
+
+  if( pSrc->a[iFrom].pTab && pSrc->a[iFrom].pTab->isTransient ){
+    sqliteDeleteTable(0, pSrc->a[iFrom].pTab);
+  }
+  pSrc->a[iFrom].pTab = pSubSrc->a[0].pTab;
+  pSubSrc->a[0].pTab = 0;
+  assert( pSrc->a[iFrom].pSelect==pSub );
+  pSrc->a[iFrom].pSelect = pSubSrc->a[0].pSelect;
+  pSubSrc->a[0].pSelect = 0;
+  sqliteSelectDelete(pSub);
+  return 1;
+}
+
+/*
+** Analyze the SELECT statement passed in as an argument to see if it
+** is a simple min() or max() query.  If it is and this query can be
+** satisfied using a single seek to the beginning or end of an index,
+** then generate the code for this SELECT and return 1.  If this is not a 
+** simple min() or max() query, then return 0;
+**
+** A simply min() or max() query looks like this:
+**
+**    SELECT min(a) FROM table;
+**    SELECT max(a) FROM table;
+**
+** The query may have only a single table in its FROM argument.  There
+** can be no GROUP BY or HAVING or WHERE clauses.  The result set must
+** be the min() or max() of a single column of the table.  The column
+** in the min() or max() function must be indexed.
+**
+** The parameters to this routine are the same as for sqliteSelect().
+** See the header comment on that routine for additional information.
+*/
+static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
+  Expr *pExpr;
+  int iCol;
+  Table *pTab;
+  Index *pIdx;
+  int base;
+  Vdbe *v;
+  int openOp;
+  int seekOp;
+  int cont;
+  ExprList eList;
+  struct ExprList_item eListItem;
+
+  /* Check to see if this query is a simple min() or max() query.  Return
+  ** zero if it is  not.
+  */
+  if( p->pGroupBy || p->pHaving || p->pWhere ) return 0;
+  if( p->pSrc->nSrc!=1 ) return 0;
+  if( p->pEList->nExpr!=1 ) return 0;
+  pExpr = p->pEList->a[0].pExpr;
+  if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
+  if( pExpr->pList==0 || pExpr->pList->nExpr!=1 ) return 0;
+  if( pExpr->token.n!=3 ) return 0;
+  if( sqliteStrNICmp(pExpr->token.z,"min",3)==0 ){
+    seekOp = OP_Rewind;
+  }else if( sqliteStrNICmp(pExpr->token.z,"max",3)==0 ){
+    seekOp = OP_Last;
+  }else{
+    return 0;
+  }
+  pExpr = pExpr->pList->a[0].pExpr;
+  if( pExpr->op!=TK_COLUMN ) return 0;
+  iCol = pExpr->iColumn;
+  pTab = p->pSrc->a[0].pTab;
+
+  /* If we get to here, it means the query is of the correct form.
+  ** Check to make sure we have an index and make pIdx point to the
+  ** appropriate index.  If the min() or max() is on an INTEGER PRIMARY
+  ** key column, no index is necessary so set pIdx to NULL.  If no
+  ** usable index is found, return 0.
+  */
+  if( iCol<0 ){
+    pIdx = 0;
+  }else{
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      assert( pIdx->nColumn>=1 );
+      if( pIdx->aiColumn[0]==iCol ) break;
+    }
+    if( pIdx==0 ) return 0;
+  }
+
+  /* Identify column names if we will be using the callback.  This
+  ** step is skipped if the output is going to a table or a memory cell.
+  */
+  v = sqliteGetVdbe(pParse);
+  if( v==0 ) return 0;
+  if( eDest==SRT_Callback ){
+    generateColumnNames(pParse, p->base, p->pSrc, p->pEList);
+    generateColumnTypes(pParse, p->base, p->pSrc, p->pEList);
+  }
+
+  /* Generating code to find the min or the max.  Basically all we have
+  ** to do is find the first or the last entry in the chosen index.  If
+  ** the min() or max() is on the INTEGER PRIMARY KEY, then find the first
+  ** or last entry in the main table.
+  */
+  if( !pParse->schemaVerified && (pParse->db->flags & SQLITE_InTrans)==0 ){
+    sqliteVdbeAddOp(v, OP_VerifyCookie, pParse->db->schema_cookie, 0);
+    pParse->schemaVerified = 1;
+  }
+  openOp = pTab->isTemp ? OP_OpenAux : OP_Open;
+  base = p->base;
+  sqliteVdbeAddOp(v, openOp, base, pTab->tnum);
+  sqliteVdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
+  if( pIdx==0 ){
+    sqliteVdbeAddOp(v, seekOp, base, 0);
+  }else{
+    sqliteVdbeAddOp(v, openOp, base+1, pIdx->tnum);
+    sqliteVdbeChangeP3(v, -1, pIdx->zName, P3_STATIC);
+    sqliteVdbeAddOp(v, seekOp, base+1, 0);
+    sqliteVdbeAddOp(v, OP_IdxRecno, base+1, 0);
+    sqliteVdbeAddOp(v, OP_Close, base+1, 0);
+    sqliteVdbeAddOp(v, OP_MoveTo, base, 0);
+  }
+  eList.nExpr = 1;
+  memset(&eListItem, 0, sizeof(eListItem));
+  eList.a = &eListItem;
+  eList.a[0].pExpr = pExpr;
+  cont = sqliteVdbeMakeLabel(v);
+  selectInnerLoop(pParse, p, &eList, 0, 0, 0, -1, eDest, iParm, cont, cont);
+  sqliteVdbeResolveLabel(v, cont);
+  sqliteVdbeAddOp(v, OP_Close, base, 0);
+  return 1;
+}
+
+/*
+** Generate code for the given SELECT statement.
+**
+** The results are distributed in various ways depending on the
+** value of eDest and iParm.
+**
+**     eDest Value       Result
+**     ------------    -------------------------------------------
+**     SRT_Callback    Invoke the callback for each row of the result.
+**
+**     SRT_Mem         Store first result in memory cell iParm
+**
+**     SRT_Set         Store results as keys of a table with cursor iParm
+**
+**     SRT_Union       Store results as a key in a temporary table iParm
+**
+**     SRT_Except      Remove results form the temporary table iParm.
+**
+**     SRT_Table       Store results in temporary table iParm
+**
+** The table above is incomplete.  Additional eDist value have be added
+** since this comment was written.  See the selectInnerLoop() function for
+** a complete listing of the allowed values of eDest and their meanings.
+**
+** This routine returns the number of errors.  If any errors are
+** encountered, then an appropriate error message is left in
+** pParse->zErrMsg.
+**
+** This routine does NOT free the Select structure passed in.  The
+** calling function needs to do that.
+**
+** The pParent, parentTab, and *pParentAgg fields are filled in if this
+** SELECT is a subquery.  This routine may try to combine this SELECT
+** with its parent to form a single flat query.  In so doing, it might
+** change the parent query from a non-aggregate to an aggregate query.
+** For that reason, the pParentAgg flag is passed as a pointer, so it
+** can be changed.
+**
+** Example 1:   The meaning of the pParent parameter.
+**
+**    SELECT * FROM t1 JOIN (SELECT x, count(*) FROM t2) JOIN t3;
+**    \                      \_______ subquery _______/        /
+**     \                                                      /
+**      \____________________ outer query ___________________/
+**
+** This routine is called for the outer query first.   For that call,
+** pParent will be NULL.  During the processing of the outer query, this 
+** routine is called recursively to handle the subquery.  For the recursive
+** call, pParent will point to the outer query.  Because the subquery is
+** the second element in a three-way join, the parentTab parameter will
+** be 1 (the 2nd value of a 0-indexed array.)
+*/
+int sqliteSelect(
+  Parse *pParse,         /* The parser context */
+  Select *p,             /* The SELECT statement being coded. */
+  int eDest,             /* How to dispose of the results */
+  int iParm,             /* A parameter used by the eDest disposal method */
+  Select *pParent,       /* Another SELECT for which this is a sub-query */
+  int parentTab,         /* Index in pParent->pSrc of this query */
+  int *pParentAgg        /* True if pParent uses aggregate functions */
+){
+  int i;
+  WhereInfo *pWInfo;
+  Vdbe *v;
+  int isAgg = 0;         /* True for select lists like "count(*)" */
+  ExprList *pEList;      /* List of columns to extract. */
+  SrcList *pTabList;     /* List of tables to select from */
+  Expr *pWhere;          /* The WHERE clause.  May be NULL */
+  ExprList *pOrderBy;    /* The ORDER BY clause.  May be NULL */
+  ExprList *pGroupBy;    /* The GROUP BY clause.  May be NULL */
+  Expr *pHaving;         /* The HAVING clause.  May be NULL */
+  int isDistinct;        /* True if the DISTINCT keyword is present */
+  int distinct;          /* Table to use for the distinct set */
+  int base;              /* First cursor available for use */
+  int rc = 1;            /* Value to return from this function */
+
+  if( sqlite_malloc_failed || pParse->nErr || p==0 ) return 1;
+  if( sqliteAuthCheck(pParse, SQLITE_SELECT, 0, 0) ) return 1;
+
+  /* If there is are a sequence of queries, do the earlier ones first.
+  */
+  if( p->pPrior ){
+    return multiSelect(pParse, p, eDest, iParm);
+  }
+
+  /* Make local copies of the parameters for this query.
+  */
+  pTabList = p->pSrc;
+  pWhere = p->pWhere;
+  pOrderBy = p->pOrderBy;
+  pGroupBy = p->pGroupBy;
+  pHaving = p->pHaving;
+  isDistinct = p->isDistinct;
+
+  /* Allocate a block of VDBE cursors, one for each table in the FROM clause.
+  ** The WHERE processing requires that the cursors for the tables in the
+  ** FROM clause be consecutive.
+  */
+  base = p->base = pParse->nTab;
+  pParse->nTab += pTabList->nSrc;
+
+  /* 
+  ** Do not even attempt to generate any code if we have already seen
+  ** errors before this routine starts.
+  */
+  if( pParse->nErr>0 ) goto select_end;
+
+  /* Expand any "*" terms in the result set.  (For example the "*" in
+  ** "SELECT * FROM t1")  The fillInColumnlist() routine also does some
+  ** other housekeeping - see the header comment for details.
+  */
+  if( fillInColumnList(pParse, p) ){
+    goto select_end;
+  }
+  pWhere = p->pWhere;
+  pEList = p->pEList;
+  if( pEList==0 ) goto select_end;
+
+  /* If writing to memory or generating a set
+  ** only a single column may be output.
+  */
+  if( (eDest==SRT_Mem || eDest==SRT_Set) && pEList->nExpr>1 ){
+    sqliteSetString(&pParse->zErrMsg, "only a single result allowed for "
+       "a SELECT that is part of an expression", 0);
+    pParse->nErr++;
+    goto select_end;
+  }
+
+  /* ORDER BY is ignored for some destinations.
+  */
+  switch( eDest ){
+    case SRT_Union:
+    case SRT_Except:
+    case SRT_Discard:
+      pOrderBy = 0;
+      break;
+    default:
+      break;
+  }
+
+  /* At this point, we should have allocated all the cursors that we
+  ** need to handle subquerys and temporary tables.  
+  **
+  ** Resolve the column names and do a semantics check on all the expressions.
+  */
+  for(i=0; i<pEList->nExpr; i++){
+    if( sqliteExprResolveIds(pParse, base, pTabList, 0, pEList->a[i].pExpr) ){
+      goto select_end;
+    }
+    if( sqliteExprCheck(pParse, pEList->a[i].pExpr, 1, &isAgg) ){
+      goto select_end;
+    }
+  }
+  if( pWhere ){
+    if( sqliteExprResolveIds(pParse, base, pTabList, pEList, pWhere) ){
+      goto select_end;
+    }
+    if( sqliteExprCheck(pParse, pWhere, 0, 0) ){
+      goto select_end;
+    }
+    sqliteOracle8JoinFixup(base, pTabList, pWhere);
+  }
+  if( pHaving ){
+    if( pGroupBy==0 ){
+      sqliteSetString(&pParse->zErrMsg, "a GROUP BY clause is required "
+         "before HAVING", 0);
+      pParse->nErr++;
+      goto select_end;
+    }
+    if( sqliteExprResolveIds(pParse, base, pTabList, pEList, pHaving) ){
+      goto select_end;
+    }
+    if( sqliteExprCheck(pParse, pHaving, 1, &isAgg) ){
+      goto select_end;
+    }
+  }
+  if( pOrderBy ){
+    for(i=0; i<pOrderBy->nExpr; i++){
+      int iCol;
+      Expr *pE = pOrderBy->a[i].pExpr;
+      if( sqliteExprIsInteger(pE, &iCol) && iCol>0 && iCol<=pEList->nExpr ){
+        sqliteExprDelete(pE);
+        pE = pOrderBy->a[i].pExpr = sqliteExprDup(pEList->a[iCol-1].pExpr);
+      }
+      if( sqliteExprResolveIds(pParse, base, pTabList, pEList, pE) ){
+        goto select_end;
+      }
+      if( sqliteExprCheck(pParse, pE, isAgg, 0) ){
+        goto select_end;
+      }
+      if( sqliteExprIsConstant(pE) ){
+        if( sqliteExprIsInteger(pE, &iCol)==0 ){
+          sqliteSetString(&pParse->zErrMsg, 
+               "ORDER BY terms must not be non-integer constants", 0);
+          pParse->nErr++;
+          goto select_end;
+        }else if( iCol<=0 || iCol>pEList->nExpr ){
+          char zBuf[2000];
+          sprintf(zBuf,"ORDER BY column number %d out of range - should be "
+             "between 1 and %d", iCol, pEList->nExpr);
+          sqliteSetString(&pParse->zErrMsg, zBuf, 0);
+          pParse->nErr++;
+          goto select_end;
+        }
+      }
+    }
+  }
+  if( pGroupBy ){
+    for(i=0; i<pGroupBy->nExpr; i++){
+      int iCol;
+      Expr *pE = pGroupBy->a[i].pExpr;
+      if( sqliteExprIsInteger(pE, &iCol) && iCol>0 && iCol<=pEList->nExpr ){
+        sqliteExprDelete(pE);
+        pE = pGroupBy->a[i].pExpr = sqliteExprDup(pEList->a[iCol-1].pExpr);
+      }
+      if( sqliteExprResolveIds(pParse, base, pTabList, pEList, pE) ){
+        goto select_end;
+      }
+      if( sqliteExprCheck(pParse, pE, isAgg, 0) ){
+        goto select_end;
+      }
+      if( sqliteExprIsConstant(pE) ){
+        if( sqliteExprIsInteger(pE, &iCol)==0 ){
+          sqliteSetString(&pParse->zErrMsg, 
+               "GROUP BY terms must not be non-integer constants", 0);
+          pParse->nErr++;
+          goto select_end;
+        }else if( iCol<=0 || iCol>pEList->nExpr ){
+          char zBuf[2000];
+          sprintf(zBuf,"GROUP BY column number %d out of range - should be "
+             "between 1 and %d", iCol, pEList->nExpr);
+          sqliteSetString(&pParse->zErrMsg, zBuf, 0);
+          pParse->nErr++;
+          goto select_end;
+        }
+      }
+    }
+  }
+
+  /* Check for the special case of a min() or max() function by itself
+  ** in the result set.
+  */
+  if( simpleMinMaxQuery(pParse, p, eDest, iParm) ){
+    rc = 0;
+    goto select_end;
+  }
+
+  /* Begin generating code.
+  */
+  v = sqliteGetVdbe(pParse);
+  if( v==0 ) goto select_end;
+
+  /* Identify column names if we will be using them in a callback.  This
+  ** step is skipped if the output is going to some other destination.
+  */
+  if( eDest==SRT_Callback ){
+    generateColumnNames(pParse, p->base, pTabList, pEList);
+  }
+
+  /* Set the limiter
+  */
+  if( p->nLimit<=0 ){
+    p->nLimit = -1;
+    p->nOffset = 0;
+  }else{
+    int iMem = pParse->nMem++;
+    sqliteVdbeAddOp(v, OP_Integer, -p->nLimit, 0);
+    sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
+    p->nLimit = iMem;
+    if( p->nOffset<=0 ){
+      p->nOffset = 0;
+    }else{
+      iMem = pParse->nMem++;
+      sqliteVdbeAddOp(v, OP_Integer, -p->nOffset, 0);
+      sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
+      p->nOffset = iMem;
+    }
+  }
+
+  /* Generate code for all sub-queries in the FROM clause
+  */
+  for(i=0; i<pTabList->nSrc; i++){
+    if( pTabList->a[i].pSelect==0 ) continue;
+    sqliteSelect(pParse, pTabList->a[i].pSelect, SRT_TempTable, base+i,
+                 p, i, &isAgg);
+    pTabList = p->pSrc;
+    pWhere = p->pWhere;
+    if( eDest==SRT_Callback ){
+      pOrderBy = p->pOrderBy;
+    }
+    pGroupBy = p->pGroupBy;
+    pHaving = p->pHaving;
+    isDistinct = p->isDistinct;
+  }
+
+  /* Check to see if this is a subquery that can be "flattened" into its parent.
+  ** If flattening is a possiblity, do so and return immediately.  
+  */
+  if( pParent && pParentAgg &&
+      flattenSubquery(pParse, pParent, parentTab, *pParentAgg, isAgg) ){
+    if( isAgg ) *pParentAgg = 1;
+    return rc;
+  }
+
+  /* Identify column types if we will be using a callback.  This
+  ** step is skipped if the output is going to a destination other
+  ** than a callback.
+  */
+  if( eDest==SRT_Callback ){
+    generateColumnTypes(pParse, p->base, pTabList, pEList);
+  }
+
+  /* If the output is destined for a temporary table, open that table.
+  */
+  if( eDest==SRT_TempTable ){
+    sqliteVdbeAddOp(v, OP_OpenTemp, iParm, 0);
+  }
+
+  /* Do an analysis of aggregate expressions.
+  */
+  sqliteAggregateInfoReset(pParse);
+  if( isAgg || pGroupBy ){
+    assert( pParse->nAgg==0 );
+    isAgg = 1;
+    for(i=0; i<pEList->nExpr; i++){
+      if( sqliteExprAnalyzeAggregates(pParse, pEList->a[i].pExpr) ){
+        goto select_end;
+      }
+    }
+    if( pGroupBy ){
+      for(i=0; i<pGroupBy->nExpr; i++){
+        if( sqliteExprAnalyzeAggregates(pParse, pGroupBy->a[i].pExpr) ){
+          goto select_end;
+        }
+      }
+    }
+    if( pHaving && sqliteExprAnalyzeAggregates(pParse, pHaving) ){
+      goto select_end;
+    }
+    if( pOrderBy ){
+      for(i=0; i<pOrderBy->nExpr; i++){
+        if( sqliteExprAnalyzeAggregates(pParse, pOrderBy->a[i].pExpr) ){
+          goto select_end;
+        }
+      }
+    }
+  }
+
+  /* Reset the aggregator
+  */
+  if( isAgg ){
+    sqliteVdbeAddOp(v, OP_AggReset, 0, pParse->nAgg);
+    for(i=0; i<pParse->nAgg; i++){
+      FuncDef *pFunc;
+      if( (pFunc = pParse->aAgg[i].pFunc)!=0 && pFunc->xFinalize!=0 ){
+        sqliteVdbeAddOp(v, OP_AggInit, 0, i);
+        sqliteVdbeChangeP3(v, -1, (char*)pFunc, P3_POINTER);
+      }
+    }
+    if( pGroupBy==0 ){
+      sqliteVdbeAddOp(v, OP_String, 0, 0);
+      sqliteVdbeAddOp(v, OP_AggFocus, 0, 0);
+    }
+  }
+
+  /* Initialize the memory cell to NULL
+  */
+  if( eDest==SRT_Mem ){
+    sqliteVdbeAddOp(v, OP_String, 0, 0);
+    sqliteVdbeAddOp(v, OP_MemStore, iParm, 1);
+  }
+
+  /* Open a temporary table to use for the distinct set.
+  */
+  if( isDistinct ){
+    distinct = pParse->nTab++;
+    sqliteVdbeAddOp(v, OP_OpenTemp, distinct, 1);
+  }else{
+    distinct = -1;
+  }
+
+  /* Begin the database scan
+  */
+  pWInfo = sqliteWhereBegin(pParse, p->base, pTabList, pWhere, 0, 
+                            pGroupBy ? 0 : &pOrderBy);
+  if( pWInfo==0 ) goto select_end;
+
+  /* Use the standard inner loop if we are not dealing with
+  ** aggregates
+  */
+  if( !isAgg ){
+    if( selectInnerLoop(pParse, p, pEList, 0, 0, pOrderBy, distinct, eDest,
+                    iParm, pWInfo->iContinue, pWInfo->iBreak) ){
+       goto select_end;
+    }
+  }
+
+  /* If we are dealing with aggregates, then do the special aggregate
+  ** processing.  
+  */
+  else{
+    if( pGroupBy ){
+      int lbl1;
+      for(i=0; i<pGroupBy->nExpr; i++){
+        sqliteExprCode(pParse, pGroupBy->a[i].pExpr);
+      }
+      sqliteVdbeAddOp(v, OP_MakeKey, pGroupBy->nExpr, 0);
+      if( pParse->db->file_format>=4 ) sqliteAddKeyType(v, pGroupBy);
+      lbl1 = sqliteVdbeMakeLabel(v);
+      sqliteVdbeAddOp(v, OP_AggFocus, 0, lbl1);
+      for(i=0; i<pParse->nAgg; i++){
+        if( pParse->aAgg[i].isAgg ) continue;
+        sqliteExprCode(pParse, pParse->aAgg[i].pExpr);
+        sqliteVdbeAddOp(v, OP_AggSet, 0, i);
+      }
+      sqliteVdbeResolveLabel(v, lbl1);
+    }
+    for(i=0; i<pParse->nAgg; i++){
+      Expr *pE;
+      int j;
+      if( !pParse->aAgg[i].isAgg ) continue;
+      pE = pParse->aAgg[i].pExpr;
+      assert( pE->op==TK_AGG_FUNCTION );
+      if( pE->pList ){
+        for(j=0; j<pE->pList->nExpr; j++){
+          sqliteExprCode(pParse, pE->pList->a[j].pExpr);
+        }
+      }
+      sqliteVdbeAddOp(v, OP_Integer, i, 0);
+      sqliteVdbeAddOp(v, OP_AggFunc, 0, pE->pList ? pE->pList->nExpr : 0);
+      assert( pParse->aAgg[i].pFunc!=0 );
+      assert( pParse->aAgg[i].pFunc->xStep!=0 );
+      sqliteVdbeChangeP3(v, -1, (char*)pParse->aAgg[i].pFunc, P3_POINTER);
+    }
+  }
+
+  /* End the database scan loop.
+  */
+  sqliteWhereEnd(pWInfo);
+
+  /* If we are processing aggregates, we need to set up a second loop
+  ** over all of the aggregate values and process them.
+  */
+  if( isAgg ){
+    int endagg = sqliteVdbeMakeLabel(v);
+    int startagg;
+    startagg = sqliteVdbeAddOp(v, OP_AggNext, 0, endagg);
+    pParse->useAgg = 1;
+    if( pHaving ){
+      sqliteExprIfFalse(pParse, pHaving, startagg, 1);
+    }
+    if( selectInnerLoop(pParse, p, pEList, 0, 0, pOrderBy, distinct, eDest,
+                    iParm, startagg, endagg) ){
+      goto select_end;
+    }
+    sqliteVdbeAddOp(v, OP_Goto, 0, startagg);
+    sqliteVdbeResolveLabel(v, endagg);
+    sqliteVdbeAddOp(v, OP_Noop, 0, 0);
+    pParse->useAgg = 0;
+  }
+
+  /* If there is an ORDER BY clause, then we need to sort the results
+  ** and send them to the callback one by one.
+  */
+  if( pOrderBy ){
+    generateSortTail(p, v, pEList->nExpr, eDest, iParm);
+  }
+
+
+  /* Issue a null callback if that is what the user wants.
+  */
+  if( eDest==SRT_Callback &&
+    (pParse->useCallback==0 || (pParse->db->flags & SQLITE_NullCallback)!=0)
+  ){
+    sqliteVdbeAddOp(v, OP_NullCallback, pEList->nExpr, 0);
+  }
+
+  /* The SELECT was successfully coded.   Set the return code to 0
+  ** to indicate no errors.
+  */
+  rc = 0;
+
+  /* Control jumps to here if an error is encountered above, or upon
+  ** successful coding of the SELECT.
+  */
+select_end:
+  sqliteAggregateInfoReset(pParse);
+  return rc;
+}