ALTER TRIGGER (Transact-SQL)

Artigo
12/03/2008

Modifies the definition of a DML, DDL, or logon trigger that was previously created by the CREATE TRIGGER statement. Triggers are created by using CREATE TRIGGER. They can be created directly from Transact-SQL statements or from methods of assemblies that are created in the Microsoft .NET Framework common language runtime (CLR) and uploaded to an instance of SQL Server. For more information about the parameters that are used in the ALTER TRIGGER statement, see CREATE TRIGGER (Transact-SQL).

Topic link icon Transact-SQL Syntax Conventions

Syntax

Trigger on an INSERT, UPDATE, or DELETE statement to a table or view (DML Trigger)
ALTER TRIGGER schema_name.trigger_name 
ON ( table | view ) 
[ WITH <dml_trigger_option> [ ,...n ] ]
( FOR | AFTER | INSTEAD OF ) 
{ [ DELETE ] [ , ] [ INSERT ] [ , ] [ UPDATE ] } 
[ NOT FOR REPLICATION ] 
AS { sql_statement [ ; ] [ ...n ] | EXTERNAL NAME <method specifier> [ ; ] } 

<dml_trigger_option> ::=
    [ ENCRYPTION ]
    [ <EXECUTE AS Clause> ]

<method_specifier> ::=
        assembly_name.class_name.method_name

Trigger on a CREATE, ALTER, DROP, GRANT, DENY, REVOKE, or UPDATE statement (DDL Trigger)

ALTER TRIGGER trigger_name 
ON { DATABASE | ALL SERVER } 
[ WITH <ddl_trigger_option> [ ,...n ] ]
{ FOR | AFTER } { event_type [ ,...n ] | event_group } 
AS { sql_statement [ ; ] | EXTERNAL NAME <method specifier> 
[ ; ] }

} 

<ddl_trigger_option> ::=
    [ ENCRYPTION ]
    [ <EXECUTE AS Clause> ]

<method_specifier> ::=
        assembly_name.class_name.method_name

Trigger on a LOGON event (Logon Trigger)
ALTER TRIGGER trigger_name 
ON ALL SERVER 
[ WITH <logon_trigger_option> [ ,...n ] ]
{ FOR | AFTER } LOGON 
AS { sql_statement  [ ; ] [ ,...n ] | EXTERNAL NAME < method specifier >  [ ; ] }

<logon_trigger_option> ::=
    [ ENCRYPTION ]
    [ EXECUTE AS Clause ]

<method_specifier> ::=
    assembly_name.class_name.method_name

Arguments

schema_name
Is the name of the schema to which a DML trigger belongs. DML triggers are scoped to the schema of the table or view on which they are created. schema_name is optional only if the DML trigger and its corresponding table or view belong to the default schema. schema_name cannot be specified for DDL or logon triggers.

trigger_name
Is the existing trigger to modify.

table | view
Is the table or view on which the DML trigger is executed. Specifying the fully-qualified name of the table or view is optional.

DATABASE
Applies the scope of a DDL trigger to the current database. If specified, the trigger fires whenever event_type or event_group occurs in the current database.

ALL SERVER
Applies the scope of a DDL or logon trigger to the current server. If specified, the trigger fires whenever event_type or event_group occurs anywhere in the current server.

WITH ENCRYPTION
Encrypts the syscomments entries that contain the text of the ALTER TRIGGER statement. Using WITH ENCRYPTION prevents the trigger from being published as part of SQL Server replication. WITH ENCRYPTION cannot be specified for CLR triggers.

Note

If a trigger is created by using WITH ENCRYPTION, it must be specified again in the ALTER TRIGGER statement for this option to remain enabled.

EXECUTE AS
Specifies the security context under which the trigger is executed. Enables you to control the user account the instance of SQL Server uses to validate permissions on any database objects that are referenced by the trigger.

For more information, see EXECUTE AS Clause (Transact-SQL).

AFTER
Specifies that the trigger is fired only after the triggering SQL statement is executed successfully. All referential cascade actions and constraint checks also must have been successful before this trigger fires.

AFTER is the default, if only the FOR keyword is specified.

DML AFTER triggers may be defined only on tables.

INSTEAD OF
Specifies that the DML trigger is executed instead of the triggering SQL statement, therefore, overriding the actions of the triggering statements. INSTEAD OF cannot be specified for DDL or logon triggers.

At most, one INSTEAD OF trigger per INSERT, UPDATE, or DELETE statement can be defined on a table or view. However, you can define views on views where each view has its own INSTEAD OF trigger.

INSTEAD OF triggers are not allowed on views created by using WITH CHECK OPTION. SQL Server raises an error when an INSTEAD OF trigger is added to a view for which WITH CHECK OPTION was specified. The user must remove that option using ALTER VIEW before defining the INSTEAD OF trigger.

{ [ DELETE ] [ , ] [ INSERT ] [ , ] [ UPDATE ] } | { [INSERT ] [ , ] [ UPDATE ] }
Specifies the data modification statements, when tried against this table or view, activate the DML trigger. At least one option must be specified. Any combination of these in any order is allowed in the trigger definition. If more than one option is specified, separate the options with commas.

For INSTEAD OF triggers, the DELETE option is not allowed on tables that have a referential relationship specifying a cascade action ON DELETE. Similarly, the UPDATE option is not allowed on tables that have a referential relationship specifying a cascade action ON UPDATE. For more information, see ALTER TABLE (Transact-SQL).

event_type
Is the name of a Transact-SQL language event that, after execution, causes a DDL trigger to fire. Events that are valid for use in DDL triggers are listed in DDL Events for Use with DDL Triggers.

event_group
Is the name of a predefined grouping of Transact-SQL language events. The DDL trigger fires after execution of any Transact-SQL language event that belongs to event_group. Event groups that are valid for use in DDL triggers are listed in Event Groups for Use with DDL Triggers. After ALTER TRIGGER has finished running, event_group also acts as a macroby adding the event types it covers to the sys.trigger_events catalog view.

NOT FOR REPLICATION
Indicates that the trigger should not be executed when a replication agent modifies the table involved in the trigger. For more information, see Controlling Constraints, Identities, and Triggers with NOT FOR REPLICATION.

sql_statement
Is the trigger conditions and actions.

<method_specifier>
Specifies the method of an assembly to bind with the trigger. The method must take no arguments and return void. class_name must be a valid SQL Server identifier and must exist as a class in the assembly with assembly visibility. The class cannot be a nested class.

Remarks

For more information about ALTER TRIGGER, see Remarks in CREATE TRIGGER (Transact-SQL).

DML Triggers

ALTER TRIGGER supports manually updatable views through INSTEAD OF triggers on tables and views. SQL Server applies ALTER TRIGGER the same way for all kinds of triggers (AFTER, INSTEAD-OF).

The first and last AFTER triggers to be executed on a table can be specified by using sp_settriggerorder. Only one first and one last AFTER trigger can be specified on a table. If there are other AFTER triggers on the same table, they are randomly executed.

If an ALTER TRIGGER statement changes a first or last trigger, the first or last attribute set on the modified trigger is dropped, and the order value must be reset by using sp_settriggerorder.

An AFTER trigger is executed only after the triggering SQL statement has executed successfully. This successful execution includes all referential cascade actions and constraint checks associated with the object updated or deleted. The AFTER trigger operation checks for the effects of the triggering statement and also all referential cascade UPDATE and DELETE actions that are caused by the triggering statement.

When a DELETE action to a child or referencing table is the result of a CASCADE on a DELETE from the parent table, and an INSTEAD OF trigger on DELETE is defined on that child table, the trigger is ignored and the DELETE action is executed.

DDL Triggers

Unlike DML triggers, DDL triggers are not scoped to schemas. Therefore, the OBJECT_ID, OBJECT_NAME, OBJECTPROPERTY, and OBJECTPROPERTY(EX) cannot be used when querying metadata about DDL triggers. Use the catalog views instead. For more information, see Getting Information About DDL Triggers.

Permissions

To alter a DML trigger requires ALTER permission on the table or view on which the trigger is defined.

To alter a DDL trigger defined with server scope (ON ALL SERVER) or a logon trigger requires CONTROL SERVER permission on the server. To alter a DDL trigger defined with database scope (ON DATABASE) requires ALTER ANY DATABASE DDL TRIGGER permission in the current database.

Examples

The following example creates a DML trigger that prints a user-defined message to the client when a user tries to add or change data in the SalesPersonQuotaHistory table. The trigger is then modified by using ALTER TRIGGER to apply the trigger only on INSERT activities. This trigger is helpful because it reminds the user that updates or inserts rows into this table to also notify the Compensation department.

USE AdventureWorks;
GO
IF OBJECT_ID(N'Sales.bonus_reminder', N'TR') IS NOT NULL
    DROP TRIGGER Sales.bonus_reminder;
GO
CREATE TRIGGER Sales.bonus_reminder
ON Sales.SalesPersonQuotaHistory
WITH ENCRYPTION
AFTER INSERT, UPDATE 
AS RAISERROR ('Notify Compensation', 16, 10);
GO
-- Now, change the trigger.
USE AdventureWorks;
GO
ALTER TRIGGER Sales.bonus_reminder
ON Sales.SalesPersonQuotaHistory
AFTER INSERT
AS RAISERROR ('Notify Compensation', 16, 10);
GO

Change History

Release	History
12 December 2006	New content Added syntax, arguments, and permissions information about logon triggers, which are introduced in SQL Server 2005 Service Pack 2.
5 December 2005	New content: Clarified when the schema_name argument must be specified.

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ALTER TRIGGER (Transact-SQL)

Syntax

Arguments

Remarks

DML Triggers

DDL Triggers

Permissions

Examples

See Also

Reference

Other Resources

Help and Information

Change History

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