<Chapter>

<Title>Commands</Title>

<!-- allfiles.sgml

-

- Complete list of usable sgml source files in this directory.

-

- -->

<Para>

</Para>

<!entity intro-ref system "intro-ref.sgml">

<!entity commands system "commands.sgml">

&alterTable;

&alterUser;

&begin;

&close;

&cluster;

&commit;

&copy;

&createAggregate;

&createDatabase;

&createFunction;

&createIndex;

&createLanguage;

&createOperator;

&createRule;

&createSequence;

&createTable;

&dropFunction;

&select;

<!-- these will go into the "operators" reference chapter -->

<!entity all system "all.sgml">

<!entity any system "any.sgml">

<!entity between system "between.sgml">

<!entity in system "in.sgml">

<!entity like system "like.sgml">

</Chapter>

<!-- these will go into the "functions" reference chapter -->

<!entity avg system "avg.sgml">

<!entity cast system "cast.sgml">

<!entity charLength system "char_length.sgml">

<!entity count system "count.sgml">

<!entity currentDate system "current_date.sgml">

<!entity currentTime system "current_time.sgml">

<!entity currentTimestamp system "current_timestamp.sgml">

<!entity currentUser system "current_user.sgml">

<!entity exists system "exists.sgml">

<!entity extract system "extract.sgml">

<!entity initcap system "initcap.sgml">

<!entity lower system "lower.sgml">

<!entity lpad system "lpad.sgml">

<!entity max system "max.sgml">

<!entity min system "min.sgml">

<!entity position system "position.sgml">

<!entity rpad system "rpad.sgml">

<!entity substring system "substring.sgml">

<!entity sum system "sum.sgml">

<!entity translate system "translate.sgml">

<!entity trim system "trim.sgml">

<!entity upper system "upper.sgml">

<!-- Keep this comment at the end of the file

Local variables:

mode: sgml

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sgml-shorttag:t

sgml-minimize-attributes:nil

sgml-always-quote-attributes:t

sgml-indent-step:1

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sgml-local-catalogs:"/usr/lib/sgml/catalog"

sgml-local-ecat-files:nil

End:

<!-- these are folded into create_table.sgml

<!entity check system "check.sgml">

<!entity constraints system "constraint.sgml">

<!entity default system "default.sgml">

<!entity notNull system "not_null.sgml">

<!entity primaryKey system "primary_key.sgml">

<!entity unique system "unique.sgml">

-->

<!-- these are folded into select.sgml

<!entity groupBy system "group_by.sgml">

<!entity having system "having.sgml">

<!entity orderBy system "order_by.sgml">

<!entity union system "union.sgml">

-->

<!-- these are in the "commands" reference chapter -->

<!entity alterTable system "alter_table.sgml">

<!entity alterUser system "alter_user.sgml">

<!entity begin system "begin.sgml">

<!entity close system "close.sgml">

<!entity cluster system "cluster.sgml">

<!entity commit system "commit.sgml">

<!entity copy system "copy.sgml">

<!entity createAggregate system "create_aggregate.sgml">

<!entity createDatabase system "create_database.sgml">

<!entity createFunction system "create_function.sgml">

<!entity createIndex system "create_index.sgml">

<!entity createLanguage system "create_language.sgml">

<!entity createOperator system "create_operator.sgml">

<!entity createRule system "create_rule.sgml">

<!entity createSequence system "create_sequence.sgml">

<!entity createTable system "create_table.sgml">

<!entity createTrigger system "create_trigger.sgml">

<!entity createType system "create_type.sgml">

<!entity createUser system "create_user.sgml">

<!entity createView system "create_view.sgml">

<!entity declare system "declare.sgml">

<!entity delete system "delete.sgml">

<!entity dropAggregate system "drop_aggregate.sgml">

<!entity dropDatabase system "drop_database.sgml">

<!entity dropFunction system "drop_function.sgml">

<!entity dropIndex system "drop_index.sgml">

<!entity dropLanguage system "drop_language.sgml">

<!entity dropOperator system "drop_operator.sgml">

<!entity dropRule system "drop_rule.sgml">

<!entity dropSequence system "drop_sequence.sgml">

<!entity dropTable system "drop_table.sgml">

<!entity dropTrigger system "drop_trigger.sgml">

<!entity dropType system "drop_type.sgml">

<!entity dropUser system "drop_user.sgml">

<!entity dropView system "drop_view.sgml">

<!entity explain system "explain.sgml">

<!entity fetch system "fetch.sgml">

<!entity grant system "grant.sgml">

<!entity insert system "insert.sgml">

<!entity listen system "listen.sgml">

<!entity load system "load.sgml">

<!entity lock system "lock.sgml">

<!entity move system "move.sgml">

<!entity notify system "notify.sgml">

<!entity reset system "reset.sgml">

<!entity revoke system "revoke.sgml">

<!entity rollback system "rollback.sgml">

<!entity select system "select.sgml">

<!entity set system "set.sgml">

<!entity show system "show.sgml">

<!entity update system "update.sgml">

<!entity vacuum system "vacuum.sgml">

<REFENTRY ID="SQL-CREATETRIGGER-1">

<REFMETA>

<REFENTRYTITLE>

CREATE TRIGGER

</REFENTRYTITLE>

<REFMISCINFO>SQL - Language Statements</REFMISCINFO>

</REFMETA>

<REFNAMEDIV>

<REFNAME>

CREATE TRIGGER

</REFNAME>

<REFPURPOSE>

CREATE TRIGGER - creates a new trigger.

</REFPURPOSE>

<REFSYNOPSISDIV>

<REFSYNOPSISDIVINFO>

<DATE>1998-04-15</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 }

EXECUTE PROCEDURE <REPLACEABLE CLASS="PARAMETER">funcname</REPLACEABLE> ( <REPLACEABLE CLASS="PARAMETER">arguments</REPLACEABLE> )

</SYNOPSIS>

<REFSECT2 ID="R2-SQL-CREATETRIGGER-1">

<REFSECT2INFO>

<DATE>1998-04-15</DATE>

</REFSECT2INFO>

<TITLE>

Inputs

</TITLE>

<PARA>

</PARA>

<VARIABLELIST>

<VARLISTENTRY>

<TERM>

</TERM>

<LISTITEM>

<PARA>

<VARIABLELIST>

<VARLISTENTRY>

<TERM>

<ReturnValue><replaceable class="parameter">name</replaceable></ReturnValue>

</TERM>

<LISTITEM>

<PARA>

The name of an existing trigger.

</PARA>

</LISTITEM>

</VARLISTENTRY>

<VARLISTENTRY>

<TERM>

<ReturnValue><replaceable class="parameter">table</replaceable></ReturnValue>

</TERM>

<LISTITEM>

<PARA>

The name of a table.

</PARA>

</LISTITEM>

</VARLISTENTRY>

<VARLISTENTRY>

<TERM>

<ReturnValue><replaceable class="parameter">event</replaceable></ReturnValue>

</TERM>

<LISTITEM>

<PARA>

One of INSERT, DELETE or UPDATE.

</PARA>

</LISTITEM>

</VARLISTENTRY>

<VARLISTENTRY>

<TERM>

<ReturnValue><replaceable class="parameter">funcname</replaceable></ReturnValue>

</TERM>

<LISTITEM>

<PARA>

A user-supplied function.

</PARA>

</LISTITEM>

</VARLISTENTRY>

</variablelist>

</LISTITEM>

</VARLISTENTRY>

</VARIABLELIST>

</REFSECT2>

<REFSECT2 ID="R2-SQL-CREATETRIGGER-2">

<REFSECT2INFO>

<DATE>1998-04-15</DATE>

</REFSECT2INFO>

<TITLE>

Outputs

</TITLE>

<PARA>

</PARA>

<VARIABLELIST>

<VARLISTENTRY>

<TERM>

</TERM>

<LISTITEM>

<PARA>

<VARIABLELIST>

<VARLISTENTRY>

<TERM>

<ReturnValue>CREATE</ReturnValue>

</TERM>

<LISTITEM>

<PARA>

This message is returned if the trigger is successfully created.

</PARA>

</LISTITEM>

</VARLISTENTRY>

</variablelist>

</LISTITEM>

</VARLISTENTRY>

</VARIABLELIST>

</REFSECT2>

</REFSYNOPSISDIV>

<REFSECT1 ID="R1-SQL-CREATETRIGGER-1">

<REFSECT1INFO>

<DATE>1998-04-15</DATE>

</REFSECT1INFO>

<TITLE>

Description

</TITLE>

<PARA>

CREATE TRIGGER will enter a new trigger into the current

data base. The trigger will be associated with the relation

<replaceable class="parameter">relname</replaceable> and will execute

the specified function <replaceable class="parameter">funcname</replaceable>.

</PARA>

<PARA>

Only the relation owner may create a trigger on this relation.

</PARA>

<PARA>

At release 6.3.2, STATEMENT triggers are not implemented.

</PARA>

<PARA>

The trigger can be specified to fire either before the

operation is attempted on a tuple (before constraints

are checked and the INSERT, UPDATE or DELETE is attempted) or

after the operation has been attempted (e.g. after constraints

are checked and the INSERT, UPDATE or DELETE has completed). If the

trigger fires before the event, the trigger may

skip the operation for the current tuple, or change the tuple

being inserted (for INSERT and UPDATE operations only). If

the trigger fires after the event, all changes, including the

last INSERTion, UPDATE or DELETion, are "visible" to the trigger.

</PARA>

<PARA>

Refer to the SPI and trigger programming guides for more

information.

</PARA>

<REFSECT2 ID="R2-SQL-CREATETRIGGER-3">

<REFSECT2INFO>

<DATE>1998-04-15</DATE>

</REFSECT2INFO>

<TITLE>

Notes

</TITLE>

<PARA>

CREATE TRIGGER statement is a PostgreSQL language extension.

</PARA>

<PARA>

Refer to the DROP TRIGGER statement for information on how to

remove triggers.

</PARA>

</REFSECT2>

<REFSECT1 ID="R1-SQL-CREATETRIGGER-2">

<TITLE>

Usage

</TITLE>

<PARA>

Check if the specified distributor code exists in the distributors

table before appending or updating a row in the table films:

</PARA>

<ProgramListing>

CREATE TRIGGER if_dist_exists

BEFORE INSERT OR UPDATE ON films FOR EACH ROW

EXECUTE PROCEDURE check_primary_key ('did', 'distributors', 'did');

</ProgramListing>

<PARA>

Before cancelling a distributor or updating its code, remove every

reference to the table films:

</PARA>

<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>

</REFSECT1>

<REFSECT1 ID="R1-SQL-CREATETRIGGER-3">

<TITLE>

Compatibility

</TITLE>

<PARA>

</PARA>

<REFSECT2 ID="R2-SQL-CREATETRIGGER-4">

<REFSECT2INFO>

<DATE>1998-04-15</DATE>

</REFSECT2INFO>

<TITLE>

SQL92

</TITLE>

<PARA>

There is no CREATE TRIGGER statement in SQL92.

</PARA>

<PARA>

The second example above may also be done by using a FOREIGN KEY

constraint as in:

</PARA>

<ProgramListing>

CREATE TABLE distributors (

did DECIMAL(3),

name VARCHAR(40),

CONSTRAINT if_film_exists FOREIGN KEY(did) REFERENCES films

ON UPDATE CASCADE ON DELETE CASCADE

);

</ProgramListing>

<PARA>

However, foreign keys are not yet implemented at version 6.3.2 of

PostgreSQL.

</PARA>

</REFENTRY>

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sgml-minimize-attributes:nil

sgml-always-quote-attributes:t

sgml-indent-step:1

sgml-indent-data:t

sgml-parent-document:nil

sgml-default-dtd-file:"../reference.ced"

sgml-exposed-tags:nil

sgml-local-catalogs:"/usr/lib/sgml/catalog"

sgml-local-ecat-files:nil

End:

-->