<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.16 2001/09/13 15:55:24 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.17 2001/09/13 18:17:44 petere Exp $
Postgres documentation
-->
<refentry id="SQL-CREATETRIGGER">
+ <docinfo>
+ <date>2001-09-13</date>
+ </docinfo>
+
<refmeta>
<refentrytitle id="SQL-CREATETRIGGER-TITLE">CREATE TRIGGER</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
<citetitle>PostgreSQL Programmer's Guide</citetitle> for more
information.
</para>
+ </refsect1>
- <refsect2 id="R2-SQL-CREATETRIGGER-3">
- <refsect2info>
- <date>1998-09-21</date>
- </refsect2info>
- <title>
- Notes
- </title>
- <para>
- <command>CREATE TRIGGER</command> is a <productname>Postgres</productname>
- language extension.
- </para>
- <para>
- Only the relation owner may create a trigger on this relation.
- </para>
- <para>
- As of the current release, STATEMENT triggers are not implemented.
- </para>
- <para>
- Refer to <command>DROP TRIGGER</command> for information on how to
- remove triggers.
- </para>
- </refsect2>
+ <refsect1 id="SQL-CREATETRIGGER-notes">
+ <title>Notes</title>
+
+ <para>
+ To create a trigger on a table, the user must have the
+ <literal>TRIGGER</literal> privilege on the table.
+ </para>
+
+ <para>
+ As of the current release, <literal>STATEMENT</literal> triggers are not implemented.
+ </para>
+
+ <para>
+ Refer to the <xref linkend="sql-droptrigger"> command for
+ information on how to remove triggers.
+ </para>
</refsect1>
<refsect1 id="R1-SQL-CREATETRIGGER-2">
- <title>
- Usage
- </title>
+ <title>Examples</title>
+
<para>
Check if the specified distributor code exists in the distributors
table before appending or updating a row in the table films:
+<programlisting>
CREATE TRIGGER if_dist_exists
BEFORE INSERT OR UPDATE ON films FOR EACH ROW
EXECUTE PROCEDURE check_primary_key ('did', 'distributors', 'did');
- </programlisting>
+</programlisting>
</para>
+
<para>
Before cancelling a distributor or updating its code, remove every
reference to the table films:
+<programlisting>
CREATE TRIGGER if_film_exists
BEFORE DELETE OR UPDATE ON distributors FOR EACH ROW
EXECUTE PROCEDURE check_foreign_key (1, 'CASCADE', 'did', 'films', 'did');
- </programlisting>
+</programlisting>
</para>
- </refsect1>
-
- <refsect1 id="R1-SQL-CREATETRIGGER-3">
- <title>
- Compatibility
- </title>
-
- <refsect2 id="R2-SQL-CREATETRIGGER-4">
- <refsect2info>
- <date>1998-09-21</date>
- </refsect2info>
- <title>
- SQL92
- </title>
- <para>
- There is no <command>CREATE TRIGGER</command> in <acronym>SQL92</acronym>.
- </para>
-
- <para>
- The second example above may also be done by using a FOREIGN KEY
- constraint as in:
+ <para>
+ The second example can also be done by using a foreign key,
+ constraint as in:
+<programlisting>
CREATE TABLE distributors (
did DECIMAL(3),
name VARCHAR(40),
FOREIGN KEY(did) REFERENCES films
ON UPDATE CASCADE ON DELETE CASCADE
);
- </programlisting>
- </para>
- </refsect2>
+</programlisting>
+ </para>
+ </refsect1>
+
+ <refsect1 id="SQL-CREATETRIGGER-compatibility">
+ <title>Compatibility</title>
+
+ <variablelist>
+ <varlistentry>
+ <term>SQL92</term>
+ <listitem>
+ <para>
+ There is no <command>CREATE TRIGGER</command> statement in <acronym>SQL92</acronym>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SQL99</term>
+ <listitem>
+ <para>
+ The <command>CREATE TRIGGER</command> statement in
+ <productname>PostgreSQL</productname> implements a subset of the
+ SQL99 standard. The following functionality is missing:
+ <itemizedlist>
+ <listitem>
+ <para>
+ SQL99 allows triggers to fire on updates to specific columns
+ (e.g., <literal>AFTER UPDATE OF col1, col2</literal>).
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ SQL99 allows you to define aliases for the <quote>old</quote>
+ and <quote>new</quote> rows or tables for use in the definiton
+ of the triggered action (e.g., <literal>CREATE TRIGGER ... ON
+ tablename REFERENCING OLD ROW AS somename NEW ROW AS
+ othername ...</literal>). Since
+ <productname>PostgreSQL</productname> allows trigger
+ procedures to be written in any number of user-defined
+ languages, access to the data is handled in a
+ language-specific way.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <productname>PostgreSQL</productname> only has row-level
+ triggers, no statement-level triggers.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <productname>PostgreSQL</productname> only allows the
+ execution of a stored procedure for the triggered action.
+ SQL99 allows the execution of a number of other SQL commands,
+ such as <command>CREATE TABLE</command> as triggered action.
+ This limitation is not hard to work around by creating a
+ stored procedure that executes these commands.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+
+ <simplelist type="inline">
+ <member><xref linkend="sql-createfunction"></member>
+ <member><xref linkend="sql-droptrigger"></member>
+ <member><citetitle>PostgreSQL Programmer's Guide</citetitle></member>
+ </simplelist>
</refsect1>
</refentry>
<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/drop_trigger.sgml,v 1.7 2001/09/03 12:57:50 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/drop_trigger.sgml,v 1.8 2001/09/13 18:17:44 petere Exp $
Postgres documentation
-->
<refentry id="SQL-DROPTRIGGER">
+ <docinfo>
+ <date>2001-09-13</date>
+ </docinfo>
+
<refmeta>
<refentrytitle id="SQL-DROPTRIGGER-TITLE">
DROP TRIGGER
<para>
<command>DROP TRIGGER</command> will remove all references to an existing
trigger definition. To execute this command the current
- user must be the owner of the trigger.
+ user must be the owner of the table for which the trigger is defined.
</para>
-
- <refsect2 id="R2-SQL-DROPTRIGGER-3">
- <refsect2info>
- <date>1998-09-22</date>
- </refsect2info>
- <title>
- Notes
- </title>
- <para>
- <command>DROP TRIGGER</command> is a <productname>Postgres</productname>
- language extension.
- </para>
- <para>
- Refer to <command>CREATE TRIGGER</command> for
- information on how to create triggers.
- </para>
- </refsect2>
</refsect1>
-
- <refsect1 id="R1-SQL-DROPTRIGGER-2">
- <title>
- Usage
- </title>
+
+ <refsect1 id="SQL-DROPTRIGGER-examples">
+ <title>Examples</title>
+
<para>
Destroy the <literal>if_dist_exists</literal> trigger
on table <literal>films</literal>:
+<programlisting>
DROP TRIGGER if_dist_exists ON films;
- </programlisting>
+</programlisting>
</para>
</refsect1>
- <refsect1 id="R1-SQL-DROPTRIGGER-3">
- <title>
- Compatibility
- </title>
+ <refsect1 id="SQL-DROPTRIGGER-compatibility">
+ <title>Compatibility</title>
- <refsect2 id="R2-SQL-DROPTRIGGER-4">
- <refsect2info>
- <date>1998-09-22</date>
- </refsect2info>
- <title>
- SQL92
- </title>
- <para>
- There is no <command>DROP TRIGGER</command> statement in
- <acronym>SQL92</acronym>.
- </para>
- </refsect2>
+ <variablelist>
+ <varlistentry>
+ <term>SQL92</term>
+ <listitem>
+ <para>
+ There is no <command>DROP TRIGGER</command> statement in
+ <acronym>SQL92</acronym>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SQL99</term>
+ <listitem>
+ <para>
+ The <command>DROP TRIGGER</command> statement in
+ <productname>PostgreSQL</productname> is incompatible with
+ SQL99. In SQL99, trigger names are not local to tables, so the
+ command is simply <literal>DROP TRIGGER
+ <replaceable>name</replaceable></literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+
+ <simplelist type="inline">
+ <member><xref linkend="sql-createtrigger"></member>
+ </simplelist>
</refsect1>
</refentry>
projects / thirdparty / postgresql.git / commitdiff
