5 files changed, 21 insertions, 0 deletions
diff --git a/lib/sqlalchemy/dialects/mssql/base.py b/lib/sqlalchemy/dialects/mssql/base.py
index c10b75c02..ec267880c 100644
--- a/lib/sqlalchemy/dialects/mssql/base.py
+++ b/lib/sqlalchemy/dialects/mssql/base.py
@@ -1532,6 +1532,9 @@ class MSSQLCompiler(compiler.SQLCompiler):
                                  fromhints=from_hints, **kw)
             for t in [from_table] + extra_froms)
 
+    def visit_empty_set_expr(self, type_):
+        return 'SELECT 1 WHERE 1!=1'
+
 
 class MSSQLStrictCompiler(MSSQLCompiler):
 
diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py
index 3aede4a05..2bb5b5beb 100644
--- a/lib/sqlalchemy/dialects/mysql/base.py
+++ b/lib/sqlalchemy/dialects/mysql/base.py
@@ -1114,6 +1114,9 @@ class MySQLCompiler(compiler.SQLCompiler):
                                  fromhints=from_hints, **kw)
             for t in [from_table] + extra_froms)
 
+    def visit_empty_set_expr(self, type_):
+        return 'SELECT 1 FROM (SELECT 1) as _empty_set WHERE 1!=1'
+
 
 class MySQLDDLCompiler(compiler.DDLCompiler):
     def get_column_specification(self, column, **kw):
diff --git a/lib/sqlalchemy/dialects/oracle/base.py b/lib/sqlalchemy/dialects/oracle/base.py
index 356c2a2bf..76ae1ced6 100644
--- a/lib/sqlalchemy/dialects/oracle/base.py
+++ b/lib/sqlalchemy/dialects/oracle/base.py
@@ -909,6 +909,9 @@ class OracleCompiler(compiler.SQLCompiler):
     def limit_clause(self, select, **kw):
         return ""
 
+    def visit_empty_set_expr(self, type_):
+        return 'SELECT 1 FROM DUAL WHERE 1!=1'
+
     def for_update_clause(self, select, **kw):
         if self.is_subquery():
             return ""
diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index c9270943b..ad15cb0ea 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -1485,6 +1485,15 @@ class PGCompiler(compiler.SQLCompiler):
                 if escape else ''
             )
 
+    def visit_empty_set_expr(self, type_, **kw):
+        # cast the empty set to the type we are comparing against.  if
+        # we are comparing against the null type, pick an arbitrary
+        # datatype for the empty set
+        if type_._isnull:
+            type_ = INTEGER()
+        return 'SELECT CAST(NULL AS %s) WHERE 1!=1' % \
+               self.dialect.type_compiler.process(type_, **kw)
+
     def render_literal_value(self, value, type_):
         value = super(PGCompiler, self).render_literal_value(value, type_)
 
diff --git a/lib/sqlalchemy/dialects/sqlite/base.py b/lib/sqlalchemy/dialects/sqlite/base.py
index cc17b6c9b..345ad901e 100644
--- a/lib/sqlalchemy/dialects/sqlite/base.py
+++ b/lib/sqlalchemy/dialects/sqlite/base.py
@@ -870,6 +870,9 @@ class SQLiteCompiler(compiler.SQLCompiler):
             self.process(binary.left, **kw),
             self.process(binary.right, **kw))
 
+    def visit_empty_set_expr(self, type_):
+        return 'SELECT 1 FROM (SELECT 1) WHERE 1!=1'
+
 
 class SQLiteDDLCompiler(compiler.DDLCompiler):