ALTER TRIGGER

Purpose

Use the ALTER TRIGGER statement to enable, disable, or compile a database trigger.

Note: This statement does not change the declaration or definition of an existing trigger. To redeclare or redefine a trigger, use the CREATE TRIGGER statement with OR REPLACE.

See Also: CREATE TRIGGER for information on creating a trigger DROP TRIGGER for information on dropping a trigger

Prerequisites

The trigger must be in your own schema or you must have ALTER ANY TRIGGER system privilege.

In addition, to alter a trigger on DATABASE, you must have the ADMINISTER DATABASE TRIGGER system privilege.

See Also: CREATE TRIGGER for more information on triggers based on DATABASE

Syntax

Keywords and Parameters

schema

Specify the schema containing the trigger. If you omit schema, Oracle assumes the trigger is in your own schema.

trigger

Specify the name of the trigger to be altered.

ENABLE

Specify ENABLE to enable the trigger. You can also use the ENABLE ALL TRIGGERS clause of ALTER TABLE to enable all triggers associated with a table.

See Also: ALTER TABLE

DISABLE

Specify DISABLE to disable the trigger. You can also use the DISABLE ALL TRIGGERS clause of ALTER TABLE to disable all triggers associated with a table.

See Also: ALTER TABLE

COMPILE

Specify COMPILE to explicitly compile the trigger, whether it is valid or invalid. Explicit recompilation eliminates the need for implicit run-time recompilation and prevents associated run-time compilation errors and performance overhead.

Oracle first recompiles objects upon which the trigger depends, if any of these objects are invalid. If Oracle recompiles the trigger successfully, the trigger becomes valid.

If recompiling the trigger results in compilation errors, then Oracle returns an error and the trigger remains invalid. You can see the associated compiler error messages with the SQL*Plus command SHOW ERRORS.

DEBUG

Specify DEBUG to instruct the PL/SQL compiler to generate and store the code for use by the PL/SQL debugger. This clause can be used for normal triggers and for instead-of triggers.

Examples

Disable Trigger Example

Consider a trigger named reorder created on the inventory table. The trigger is fired whenever an UPDATE statement reduces the number of a particular part on hand below the part's reorder point. The trigger inserts into a table of pending orders a row that contains the part number, a reorder quantity, and the current date.

When this trigger is created, Oracle enables it automatically. You can subsequently disable the trigger with the following statement:

ALTER TRIGGER reorder DISABLE;
 

When the trigger is disabled, Oracle does not fire the trigger when an UPDATE statement causes the part's inventory to fall below its reorder point.

Enable Trigger Example

After disabling the trigger, you can subsequently enable it with the following statement:

ALTER TRIGGER reorder ENABLE; 

After you reenable the trigger, Oracle fires the trigger whenever a part's inventory falls below its reorder point as a result of an UPDATE statement. It is possible that a part's inventory falls below its reorder point while the trigger was disabled. In that case, when you reenable the trigger, Oracle does not automatically fire the trigger for this part until another transaction further reduces the inventory.