diff options
Diffstat (limited to 'doc/src/sgml/ref/create_domain.sgml')
| -rw-r--r-- | doc/src/sgml/ref/create_domain.sgml | 44 |
1 files changed, 24 insertions, 20 deletions
diff --git a/doc/src/sgml/ref/create_domain.sgml b/doc/src/sgml/ref/create_domain.sgml index 5f79dc63b5..222d49da5d 100644 --- a/doc/src/sgml/ref/create_domain.sgml +++ b/doc/src/sgml/ref/create_domain.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_domain.sgml,v 1.3 2002/03/19 02:18:13 momjian Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_domain.sgml,v 1.4 2002/03/20 19:43:28 tgl Exp $ PostgreSQL documentation --> @@ -23,13 +23,14 @@ PostgreSQL documentation <date>2002-02-24</date> </refsynopsisdivinfo> <synopsis> -CREATE DOMAIN <replaceable class="parameter">domainname</replaceable> <replaceable class="parameter">data_type</replaceable> [ DEFAULT <replaceable>default_expr</> ] [ <replaceable class="PARAMETER">column_constraint</replaceable> [, ... ] ] +CREATE DOMAIN <replaceable class="parameter">domainname</replaceable> [AS] <replaceable class="parameter">data_type</replaceable> + [ DEFAULT <replaceable>default_expr</> ] + [ <replaceable class="PARAMETER">constraint</replaceable> [, ... ] ] + +where <replaceable class="PARAMETER">constraint</replaceable> is: + [ CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> ] -{ NOT NULL | NULL <!-- | UNIQUE | PRIMARY KEY | - CHECK (<replaceable class="PARAMETER">expression</replaceable>) | - REFERENCES <replaceable class="PARAMETER">reftable</replaceable> [ ( <replaceable class="PARAMETER">refcolumn</replaceable> ) ] [ MATCH FULL | MATCH PARTIAL ] - [ ON DELETE <replaceable class="parameter">action</replaceable> ] [ ON UPDATE <replaceable class="parameter">action</replaceable> ] --> } -<!-- [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] --> +{ NOT NULL | NULL } </synopsis> <refsect2 id="R2-SQL-CREATEDOMAIN-1"> @@ -67,23 +68,26 @@ CREATE DOMAIN <replaceable class="parameter">domainname</replaceable> <replaceab <replaceable>default_expr</replaceable></literal></term> <listitem> <para> - The <literal>DEFAULT</> clause assigns a default data value for - the column whose column definition it appears within. The value - is any variable-free expression (subselects and cross-references - to other columns in the current table are not allowed). The + The <literal>DEFAULT</> clause specifies a default value for + columns of the domain data type. The value + is any variable-free expression (but subselects are not allowed). + The data type of the default expression must match the data type of the domain. </para> <para> The default expression will be used in any insert operation that - does not specify a value for the domain. If there is no default + does not specify a value for the column. If there is no default for a domain, then the default is NULL. </para> <note> <para> - The default of a column will be tested before that of the domain. + If a default value is specified for a particular column, it + overrides any default associated with the domain. In turn, + the domain default overrides any default value associated with + the underlying data type. </para> </note> </listitem> @@ -93,7 +97,7 @@ CREATE DOMAIN <replaceable class="parameter">domainname</replaceable> <replaceab <term><literal>CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable></literal></term> <listitem> <para> - An optional name for a domain. If not specified, + An optional name for a constraint. If not specified, the system generates a name. </para> </listitem> @@ -103,7 +107,7 @@ CREATE DOMAIN <replaceable class="parameter">domainname</replaceable> <replaceab <term><literal>NOT NULL</></term> <listitem> <para> - The column is not allowed to contain NULL values. This is + Values of this domain are not allowed to be NULL. This is equivalent to the column constraint <literal>CHECK (<replaceable class="PARAMETER">column</replaceable> NOT NULL)</literal>. </para> @@ -114,7 +118,7 @@ CREATE DOMAIN <replaceable class="parameter">domainname</replaceable> <replaceab <term><literal>NULL</></term> <listitem> <para> - The column is allowed to contain NULL values. This is the default. + Values of this domain are allowed to be NULL. This is the default. </para> <para> @@ -175,7 +179,7 @@ CREATE DOMAIN Domains are useful for abstracting common fields between tables into a single location for maintenance. An email address column may be used in several tables, all with the same properties. Define a domain and - use that rather than setting up each tables constraints individually. + use that rather than setting up each table's constraints individually. </para> </refsect1> @@ -195,9 +199,9 @@ CREATE TABLE countrylist (id INT4, country country_code); <title>Compatibility</title> <para> - This <command>CREATE DOMAIN</command> command is a - <productname>PostgreSQL</productname> extension. CHECK and FOREIGN KEY - constraints are currently unsupported. + SQL99 defines CREATE DOMAIN, but says that the only allowed constraint + type is CHECK constraints. CHECK constraints for domains are not yet + supported by <productname>PostgreSQL</productname>. </para> </refsect1> |