diff options
Diffstat (limited to 'doc/src/sgml/ref/create_trigger.sgml')
| -rw-r--r-- | doc/src/sgml/ref/create_trigger.sgml | 87 |
1 files changed, 62 insertions, 25 deletions
diff --git a/doc/src/sgml/ref/create_trigger.sgml b/doc/src/sgml/ref/create_trigger.sgml index 67481c19a3..ac8309af2e 100644 --- a/doc/src/sgml/ref/create_trigger.sgml +++ b/doc/src/sgml/ref/create_trigger.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.29 2002/11/21 23:34:43 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.30 2002/11/23 03:59:06 momjian Exp $ PostgreSQL documentation --> @@ -21,8 +21,9 @@ PostgreSQL documentation <date>2000-03-25</date> </refsynopsisdivinfo> <synopsis> -CREATE TRIGGER <replaceable class="PARAMETER">name</replaceable> { BEFORE | AFTER } { <replaceable class="PARAMETER">event</replaceable> [OR ...] } - ON <replaceable class="PARAMETER">table</replaceable> FOR EACH { ROW | STATEMENT } +CREATE TRIGGER <replaceable class="PARAMETER">name</replaceable> { + BEFORE | AFTER } { <replaceable class="PARAMETER">event</replaceable> [ OR ... ] } + ON <replaceable class="PARAMETER">table</replaceable> [ FOR EACH { ROW | STATEMENT } ] EXECUTE PROCEDURE <replaceable class="PARAMETER">func</replaceable> ( <replaceable class="PARAMETER">arguments</replaceable> ) </synopsis> @@ -45,11 +46,26 @@ CREATE TRIGGER <replaceable class="PARAMETER">name</replaceable> { BEFORE | AFTE </para> </listitem> </varlistentry> + + <varlistentry> + <term>BEFORE</term> + <term>AFTER</term> + <listitem> + <para> + Determines whether the function is called before or after the + event. + </para> + </listitem> + </varlistentry> + <varlistentry> <term><replaceable class="parameter">event</replaceable></term> <listitem> <para> - One of INSERT, DELETE or UPDATE. + One of <command>INSERT</command>, <command>DELETE</command> or + <command>UPDATE</command>; this specifies the event that will + fire the trigger. Multiple events can be specified using + <literal>OR</literal>. </para> </listitem> </varlistentry> @@ -57,10 +73,26 @@ CREATE TRIGGER <replaceable class="PARAMETER">name</replaceable> { BEFORE | AFTE <term><replaceable class="parameter">table</replaceable></term> <listitem> <para> - The name (optionally schema-qualified) of the table the trigger is for. + The name (optionally schema-qualified) of the table the + trigger is for. </para> </listitem> </varlistentry> + + <varlistentry> + <term>FOR EACH ROW</term> + <term>FOR EACH STATEMENT</term> + + <listitem> + <para> + This specifies whether the trigger procedure should be fired + once for every row affected by the trigger event, or just once + per SQL statement. If neither is specified, <literal>FOR EACH + STATEMENT</literal> is the default. + </para> + </listitem> + </varlistentry> + <varlistentry> <term><replaceable class="parameter">func</replaceable></term> <listitem> @@ -74,11 +106,15 @@ CREATE TRIGGER <replaceable class="PARAMETER">name</replaceable> { BEFORE | AFTE <term><replaceable class="parameter">arguments</replaceable></term> <listitem> <para> - An optional comma-separated list of arguments to be provided to the - function when the trigger is executed, along with the standard trigger - data such as old and new tuple contents. The arguments are literal - string constants. Simple names and numeric constants may be written - here too, but they will all be converted to strings. + An optional comma-separated list of arguments to be provided to + the function when the trigger is executed, along with the standard + trigger data such as old and new tuple contents. The arguments + are literal string constants. Simple names and numeric constants + may be written here too, but they will all be converted to + strings. Note that these arguments are not provided as normal + function parameters (since a trigger procedure must be declared to + take zero parameters), but are instead accessed through the + <literal>TG_ARGV</literal> array. </para> </listitem> </varlistentry> @@ -121,7 +157,7 @@ CREATE TRIGGER <para> <command>CREATE TRIGGER</command> will enter a new trigger into the current - data base. The trigger will be associated with the relation + database. The trigger will be associated with the relation <replaceable class="parameter">table</replaceable> and will execute the specified function <replaceable class="parameter">func</replaceable>. </para> @@ -142,14 +178,26 @@ CREATE TRIGGER </para> <para> + A trigger that executes <literal>FOR EACH ROW</literal> of the + specified operation is called once for every row that the operation + modifies. For example, a <command>DELETE</command> that affects 10 + rows will cause any <literal>ON DELETE</literal> triggers on the + target relation to be called 10 separate times, once for each + deleted tuple. In contrast, a trigger that executes <literal>FOR + EACH STATEMENT</literal> of the specified operation only executes + once for any given operation, regardless of how many rows it + modifies. + </para> + + <para> If multiple triggers of the same kind are defined for the same event, they will be fired in alphabetical order by name. </para> <para> - <command>SELECT</command> does not modify any rows so you can not - create <command>SELECT</command> triggers. Rules and views are more - appropriate in such cases. + <command>SELECT</command> does not modify any rows so you can not + create <command>SELECT</command> triggers. Rules and views are more + appropriate in such cases. </para> <para> @@ -177,10 +225,6 @@ CREATE TRIGGER </para> <para> - As of the current release, <literal>STATEMENT</literal> triggers are not implemented. - </para> - - <para> Refer to the <xref linkend="sql-droptrigger" endterm="sql-droptrigger-title"> command for information on how to remove triggers. </para> @@ -270,13 +314,6 @@ CREATE TABLE distributors ( <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, |