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T-SQL: trigger instead of delete doesn't work when i run a bulk delete operation

Posted on 2008-10-21
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Last Modified: 2012-08-14
I have created a trigger for 'instead of delete' that gets some data from two tables, inserts part of the deleted row in a log table and then deletes the row. The trigger works when i manually delete a row from the table, the problem is that if i run a query to delete multiple rows then it only works for the last row to be deleted. So if a query is supposed to delete 5 rows and do all the operations in the trigger for each one of them, it only does it for the last one. My guess is that it's trying to run the following trigger before it is finished with the first and that is creating a problem, any ideas? code attached below.



ALTER TRIGGER trigger1
   ON TABLE1
   INSTEAD OF DELETE
AS 
BEGIN
	-- SET NOCOUNT ON added to prevent extra result sets from
	-- interfering with SELECT statements.
	SET NOCOUNT ON;
	
	DECLARE @var1		varchar(20)
	DECLARE @var2		datetime
	DECLARE @var3		datetime
	DECLARE @var4	        datetime
	DECLARE @var5		TINYINT
	DECLARE @var6		VARCHAR(10)
	
	SET @var2 = getDate()
 
	SELECT @var1 = uid, @var3 = var3, @var4 = var4, @var5 = var5 FROM DELETED	
	
	IF @var3 < 1 BEGIN 
		INSERT INTO TABLE2 (var1, var2, var3, var4, var5) 
			VALUES (@var1, @var2, @var3, @var4, @var5)
	END
	
	DELETE FROM TABLE1 WHERE uid = @var1
END

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Question by:LDIT
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3 Comments
 
LVL 32

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Daniel Wilson earned 1000 total points
ID: 22766898
A trigger fires for each transaction, not for each row.  Your trigger assumes there's only a single row.

Try this:

ALTER TRIGGER trigger1
   ON TABLE1
   INSTEAD OF DELETE
AS 
BEGIN
  INSERT INTO TABLE2 (var1, var2, var3, var4, var5)
    (Select uid, getdate(), var3, var4, var5 from DELETED Where var3 < 1)
 
  Delete From Table1
   From Table1 Inner Join Deleted on Table1.uid = deleted.uid
END

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Author Closing Comment

by:LDIT
ID: 31508239
Cool, i thought the deleted was not a table, but rather a row. So this means the deleted table holds all the deleted rows for the transaction? Thanks for the solution!
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LVL 32

Expert Comment

by:Daniel Wilson
ID: 22768187
DELETED and INSERTED are tables ... well, not real tables, but they look like tables when within a trigger.  I'm not sure of the technical term applied.

The assumption that they have only a single record is a common trigger problem.    (Yes, I've done it too ...)

All that is within MS SQL Server ... MySQL has significantly different syntax in that area, and I'm not sure exactly what it's doing there.

Glad to help!
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