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10/04/2012

TRIGGER_NESTLEVEL (Transact-SQL)

Returns the number of triggers executed for the statement that fired the trigger. TRIGGER_NESTLEVEL is used in DML and DDL triggers to determine the current level of nesting.

Topic link icon Transact-SQL Syntax Conventions

Syntax

TRIGGER_NESTLEVEL ( [ object_id ] , [ 'trigger_type' ] , [ 'trigger_event_category' ] )

Arguments

object_id
Is the object ID of a trigger. If object_id is specified, the number of times the specified trigger has been executed for the statement is returned. If object_id is not specified, the number of times all triggers have been executed for the statement is returned.
'trigger_type'
Specifies whether to apply TRIGGER_NESTLEVEL to AFTER triggers or INSTEAD OF triggers. Specify AFTER for AFTER triggers. Specify IOT for INSTEAD OF triggers. If trigger_type is specified, trigger_event_category must also be specified.
'trigger_event_category'
Specifies whether to apply TRIGGER_NESTLEVEL to DML or DDL triggers. Specify DML for DML triggers. Specify DDL for DDL triggers. If trigger_event_category is specified, trigger_type must also be specified. Note that only AFTER can be specified with DDL, because DDL triggers can only be AFTER triggers.

Remarks

When no parameters are specified, TRIGGER_NESTLEVEL returns the total number of triggers on the call stack. This includes itself. Omission of parameters can occur when a trigger executes commands causing another trigger to be fired or creates a succession of firing triggers.

To return the total number of triggers on the call stack for a particular trigger type and event category, specify object_id = 0.

TRIGGER_NESTLEVEL returns 0 if it is executed outside a trigger and any parameters are not NULL.

When any parameters are explicitly specified as NULL, a value of NULL is returned regardless of whether TRIGGER_NESTLEVEL was used within or external to a trigger.

Examples

A. Testing the nesting level of a specific DML trigger

IF ( (SELECT TRIGGER_NESTLEVEL( OBJECT_ID('xyz') , 'AFTER' , 'DML' ) ) > 5 )
   RAISERROR('Trigger xyz nested more than 5 levels.',16,-1)

B. Testing the nesting level of a specific DDL trigger

IF ( ( SELECT TRIGGER_NESTLEVEL ( ( SELECT object_id FROM sys.triggers
WHERE name = 'abc' ), 'AFTER' , 'DDL' ) ) > 5 )
   RAISERROR ('Trigger abc nested more than 5 levels.',16,-1)

C. Testing the nesting level of all triggers executed

IF ( (SELECT trigger_nestlevel() ) > 5 )
   RAISERROR
      ('This statement nested over 5 levels of triggers.',16,-1)

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