Creating Triggers v13

The CREATE TRIGGER command defines and names a trigger that will be stored in the database.

Name

CREATE TRIGGER -- define a simple trigger.

Synopsis

CREATE [ OR REPLACE ] TRIGGER <name>
  { BEFORE | AFTER | INSTEAD OF }
  { INSERT | UPDATE | DELETE | TRUNCATE }
      [ OR { INSERT | UPDATE | DELETE | TRUNCATE } ] [, ...]
    ON <table>
  [ REFERENCING { OLD AS <old> | NEW AS <new> } ...]
  [ FOR EACH ROW ]
  [ WHEN <condition> ]
  [ DECLARE
      [ PRAGMA AUTONOMOUS_TRANSACTION; ]
      <declaration>; [, ...] ]
    BEGIN
      <statement>; [, ...]
  [ EXCEPTION
    { WHEN <exception> [ OR <exception> ] [...] THEN
        <statement>; [, ...] } [, ...]
  ]
    END

Name

CREATE TRIGGER -- define a compound trigger.

Synopsis

CREATE [ OR REPLACE ] TRIGGER <name>
  FOR { INSERT | UPDATE | DELETE | TRUNCATE }
        [ OR { INSERT | UPDATE | DELETE | TRUNCATE } ] [, ...]
           ON <table>
       [ REFERENCING { OLD AS <old> | NEW AS <new>. } ...]
       [ WHEN <condition> ]
       COMPOUND TRIGGER
       [ <private_declaration>; ] ...
       [ <procedure_or_function_definition> ] ...
       <compound_trigger_definition>
         END

Where private_declaration is an identifier of a private variable that can be accessed by any procedure or function. There can be zero, one, or more private variables. private_declaration can be any of the following:

• Variable Declaration
• Record Declaration
• Collection Declaration
• REF CURSOR and Cursor Variable Declaration
• TYPE Definitions for Records, Collections, and REF CURSORs
• Exception
• Object Variable Declaration

Where procedure_or_function_definition :=

procedure_definition | function_definition

Where procedure_definition :=

PROCEDURE proc_name[ argument_list ]
  [ options_list ]
  { IS | AS }
    procedure_body
  END [ proc_name ] ;

Where procedure_body :=

[ <declaration>; ] [, ...]
BEGIN
  <statement>; [...]
[ EXCEPTION
   { WHEN <exception> [OR <exception>] [...]] THEN <statement>; }
   [...]
]

Where function_definition :=

FUNCTION func_name [ argument_list ]
  RETURN rettype [ DETERMINISTIC ]
  [ options_list ]
  { IS | AS }
    function_body
  END [ func_name ] ;

Where function_body :=

[ <declaration>; ] [, ...]
BEGIN
  <statement>; [...]
[ EXCEPTION
  { WHEN <exception> [ OR <exception> ] [...] THEN <statement>; }
  [...]
]

Where compound_trigger_definition is:

{ compound_trigger_event } { IS | AS }
  compound_trigger_body
END [ compound_trigger_event ] [ ... ]

Where compound_trigger_event:=

[ BEFORE STATEMENT | BEFORE EACH ROW | AFTER EACH ROW | AFTER STATEMENT  | INSTEAD OF EACH ROW ]

Where compound_trigger_body:=

[ <declaration>; ] [, ...]
BEGIN
  <statement>; [...]
[ EXCEPTION
   { WHEN <exception> [OR <exception>] [...] THEN <statement>; }
   [...]
]

Description

CREATE TRIGGER defines a new trigger. CREATE OR REPLACE TRIGGER will either create a new trigger, or replace an existing definition.

If you are using the CREATE TRIGGER keywords to create a new trigger, the name of the new trigger must not match any existing trigger defined on the same table. New triggers will be created in the same schema as the table on which the triggering event is defined.

If you are updating the definition of an existing trigger, use the CREATE OR REPLACE TRIGGER keywords.

When you use syntax compatible with Oracle databases to create a trigger, the trigger runs as a SECURITY DEFINER function.

Parameters

name

The name of the trigger to create.

BEFORE | AFTER

Determines whether the trigger is fired before or after the triggering event.

INSTEAD OF

INSTEAD OF trigger modifies an updatable view; the trigger will execute to update the underlying table(s) appropriately. The INSTEAD OF trigger is executed for each row of the view that is updated or modified.

INSERT | UPDATE | DELETE | TRUNCATE

Defines the triggering event.

table

The name of the table or view on which the triggering event occurs.

condition

condition is a Boolean expression that determines if the trigger will actually be executed; if condition evaluates to TRUE, the trigger will fire.

• If the simple trigger definition includes the FOR EACH ROW keywords, the WHEN clause can refer to columns of the old and/or new row values by writing OLD.column_name or NEW.column_name respectively. INSERT triggers cannot refer to OLD and DELETE triggers cannot refer to NEW.

• If the compound trigger definition includes a statement-level trigger having a WHEN clause, then the trigger is executed without evaluating the expression in the WHEN clause. Similarly, if a compound trigger definition includes a row-level trigger having a WHEN clause, then the trigger is executed if the expression evaluates to TRUE.

• If the trigger includes the INSTEAD OF keywords, it may not include a WHEN clause. A WHEN clause cannot contain subqueries.

REFERENCING { OLD AS old | NEW AS new } ...

REFERENCING clause to reference old rows and new rows, but restricted in that old may only be replaced by an identifier named old or any equivalent that is saved in all lowercase (for example, REFERENCING OLD AS old, REFERENCING OLD AS OLD, or REFERENCING OLD AS "old"). Also, new may only be replaced by an identifier named new or any equivalent that is saved in all lowercase (for example, REFERENCING NEW AS new, REFERENCING NEW AS NEW, or REFERENCING NEW AS "new").

Either one, or both phrases OLD AS old and NEW AS new may be specified in the REFERENCING clause (for example, REFERENCING NEW AS New OLD AS Old). This clause is not compatible with Oracle databases in that identifiers other than old or new may not be used.

FOR EACH ROW

Determines whether the trigger should be fired once for every row affected by the triggering event, or just once per SQL statement. If specified, the trigger is fired once for every affected row (row-level trigger), otherwise the trigger is a statement-level trigger.

PRAGMA AUTONOMOUS_TRANSACTION

PRAGMA AUTONOMOUS_TRANSACTION is the directive that sets the trigger as an autonomous transaction.

declaration

A variable, type, REF CURSOR, or subprogram declaration. If subprogram declarations are included, they must be declared after all other variable, type, and REF CURSOR declarations.

statement

An SPL program statement. Note that a DECLARE - BEGIN - END block is considered an SPL statement unto itself. Thus, the trigger body may contain nested blocks.

exception

An exception condition name such as NO_DATA_FOUND, OTHERS, etc.