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Update compatibility information.
This commit is contained in:
Peter Eisentraut
parent
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commit
a6496a2338
@ -1,9 +1,13 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.16 2001/09/13 15:55:24 petere Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.17 2001/09/13 18:17:44 petere Exp $
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Postgres documentation
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-->
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<refentry id="SQL-CREATETRIGGER">
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<docinfo>
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<date>2001-09-13</date>
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</docinfo>
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<refmeta>
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<refentrytitle id="SQL-CREATETRIGGER-TITLE">CREATE TRIGGER</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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@ -134,78 +138,55 @@ CREATE
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<citetitle>PostgreSQL Programmer's Guide</citetitle> for more
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information.
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</para>
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</refsect1>
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<refsect2 id="R2-SQL-CREATETRIGGER-3">
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<refsect2info>
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<date>1998-09-21</date>
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</refsect2info>
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<title>
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Notes
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</title>
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<para>
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<command>CREATE TRIGGER</command> is a <productname>Postgres</productname>
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language extension.
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</para>
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<para>
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Only the relation owner may create a trigger on this relation.
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</para>
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<para>
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As of the current release, STATEMENT triggers are not implemented.
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</para>
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<para>
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Refer to <command>DROP TRIGGER</command> for information on how to
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remove triggers.
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</para>
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</refsect2>
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<refsect1 id="SQL-CREATETRIGGER-notes">
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<title>Notes</title>
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<para>
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To create a trigger on a table, the user must have the
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<literal>TRIGGER</literal> privilege on the table.
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</para>
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<para>
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As of the current release, <literal>STATEMENT</literal> triggers are not implemented.
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</para>
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<para>
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Refer to the <xref linkend="sql-droptrigger"> command for
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information on how to remove triggers.
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</para>
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</refsect1>
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<refsect1 id="R1-SQL-CREATETRIGGER-2">
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<title>
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Usage
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</title>
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<title>Examples</title>
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<para>
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Check if the specified distributor code exists in the distributors
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table before appending or updating a row in the table films:
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<programlisting>
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<programlisting>
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CREATE TRIGGER if_dist_exists
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BEFORE INSERT OR UPDATE ON films FOR EACH ROW
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EXECUTE PROCEDURE check_primary_key ('did', 'distributors', 'did');
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</programlisting>
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</programlisting>
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</para>
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<para>
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Before cancelling a distributor or updating its code, remove every
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reference to the table films:
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<programlisting>
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<programlisting>
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CREATE TRIGGER if_film_exists
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BEFORE DELETE OR UPDATE ON distributors FOR EACH ROW
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EXECUTE PROCEDURE check_foreign_key (1, 'CASCADE', 'did', 'films', 'did');
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</programlisting>
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</programlisting>
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</para>
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</refsect1>
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<refsect1 id="R1-SQL-CREATETRIGGER-3">
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<title>
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Compatibility
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</title>
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<refsect2 id="R2-SQL-CREATETRIGGER-4">
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<refsect2info>
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<date>1998-09-21</date>
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</refsect2info>
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<title>
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SQL92
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</title>
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<para>
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The second example can also be done by using a foreign key,
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constraint as in:
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<para>
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There is no <command>CREATE TRIGGER</command> in <acronym>SQL92</acronym>.
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</para>
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<para>
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The second example above may also be done by using a FOREIGN KEY
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constraint as in:
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<programlisting>
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<programlisting>
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CREATE TABLE distributors (
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did DECIMAL(3),
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name VARCHAR(40),
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@ -213,9 +194,84 @@ CREATE TABLE distributors (
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FOREIGN KEY(did) REFERENCES films
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ON UPDATE CASCADE ON DELETE CASCADE
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);
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</programlisting>
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</para>
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</refsect2>
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</programlisting>
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</para>
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</refsect1>
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<refsect1 id="SQL-CREATETRIGGER-compatibility">
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<title>Compatibility</title>
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<variablelist>
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<varlistentry>
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<term>SQL92</term>
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<listitem>
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<para>
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There is no <command>CREATE TRIGGER</command> statement in <acronym>SQL92</acronym>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>SQL99</term>
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<listitem>
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<para>
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The <command>CREATE TRIGGER</command> statement in
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<productname>PostgreSQL</productname> implements a subset of the
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SQL99 standard. The following functionality is missing:
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<itemizedlist>
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<listitem>
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<para>
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SQL99 allows triggers to fire on updates to specific columns
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(e.g., <literal>AFTER UPDATE OF col1, col2</literal>).
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</para>
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</listitem>
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<listitem>
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<para>
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SQL99 allows you to define aliases for the <quote>old</quote>
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and <quote>new</quote> rows or tables for use in the definiton
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of the triggered action (e.g., <literal>CREATE TRIGGER ... ON
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tablename REFERENCING OLD ROW AS somename NEW ROW AS
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othername ...</literal>). Since
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<productname>PostgreSQL</productname> allows trigger
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procedures to be written in any number of user-defined
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languages, access to the data is handled in a
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language-specific way.
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</para>
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</listitem>
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<listitem>
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<para>
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<productname>PostgreSQL</productname> only has row-level
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triggers, no statement-level triggers.
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</para>
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</listitem>
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<listitem>
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<para>
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<productname>PostgreSQL</productname> only allows the
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execution of a stored procedure for the triggered action.
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SQL99 allows the execution of a number of other SQL commands,
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such as <command>CREATE TABLE</command> as triggered action.
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This limitation is not hard to work around by creating a
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stored procedure that executes these commands.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-createfunction"></member>
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<member><xref linkend="sql-droptrigger"></member>
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<member><citetitle>PostgreSQL Programmer's Guide</citetitle></member>
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</simplelist>
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</refsect1>
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</refentry>
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@ -1,9 +1,13 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/drop_trigger.sgml,v 1.7 2001/09/03 12:57:50 petere Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/drop_trigger.sgml,v 1.8 2001/09/13 18:17:44 petere Exp $
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Postgres documentation
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-->
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<refentry id="SQL-DROPTRIGGER">
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<docinfo>
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<date>2001-09-13</date>
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</docinfo>
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<refmeta>
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<refentrytitle id="SQL-DROPTRIGGER-TITLE">
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DROP TRIGGER
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@ -101,58 +105,58 @@ ERROR: DropTrigger: there is no trigger <replaceable class="PARAMETER">name</rep
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<para>
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<command>DROP TRIGGER</command> will remove all references to an existing
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trigger definition. To execute this command the current
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user must be the owner of the trigger.
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user must be the owner of the table for which the trigger is defined.
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</para>
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<refsect2 id="R2-SQL-DROPTRIGGER-3">
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<refsect2info>
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<date>1998-09-22</date>
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</refsect2info>
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<title>
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Notes
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</title>
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<para>
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<command>DROP TRIGGER</command> is a <productname>Postgres</productname>
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language extension.
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</para>
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<para>
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Refer to <command>CREATE TRIGGER</command> for
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information on how to create triggers.
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</para>
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</refsect2>
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</refsect1>
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<refsect1 id="R1-SQL-DROPTRIGGER-2">
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<title>
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Usage
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</title>
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<refsect1 id="SQL-DROPTRIGGER-examples">
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<title>Examples</title>
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<para>
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Destroy the <literal>if_dist_exists</literal> trigger
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on table <literal>films</literal>:
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<programlisting>
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<programlisting>
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DROP TRIGGER if_dist_exists ON films;
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</programlisting>
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</programlisting>
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</para>
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</refsect1>
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<refsect1 id="R1-SQL-DROPTRIGGER-3">
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<title>
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Compatibility
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</title>
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<refsect1 id="SQL-DROPTRIGGER-compatibility">
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<title>Compatibility</title>
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<refsect2 id="R2-SQL-DROPTRIGGER-4">
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<refsect2info>
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<date>1998-09-22</date>
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</refsect2info>
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<title>
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SQL92
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</title>
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<para>
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There is no <command>DROP TRIGGER</command> statement in
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<acronym>SQL92</acronym>.
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</para>
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</refsect2>
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<variablelist>
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<varlistentry>
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<term>SQL92</term>
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<listitem>
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<para>
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There is no <command>DROP TRIGGER</command> statement in
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<acronym>SQL92</acronym>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>SQL99</term>
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<listitem>
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<para>
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The <command>DROP TRIGGER</command> statement in
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<productname>PostgreSQL</productname> is incompatible with
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SQL99. In SQL99, trigger names are not local to tables, so the
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command is simply <literal>DROP TRIGGER
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<replaceable>name</replaceable></literal>.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-createtrigger"></member>
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</simplelist>
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</refsect1>
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</refentry>
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