SQL Trigger for multiple columns

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SQL Trigger for multiple columns - Insert / update

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Minnu

Posted Wednesday, December 05, 2012 3:00 AM

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hi Team,

I want to create a trigger, that that should fire when ever particular columns are updated/inserted.

am using below query.. is it correct way.

CREATE TRIGGER [TRG_TESTING]
ON TABLE_NAME
AFTER INSERT,UPDATE
AS
SET NOCOUNT ON
IF (UPDATE (Col1,Col2,Col3) OR
(INSERT (Col1,Col2,Col3)

DECLARE
@Var1 varchar(max),
@ID INT
---
---
--

.

Post #1392869

anthony.green

Posted Wednesday, December 05, 2012 3:34 AM

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Look at the COLUMNS_UPDATED() clause

http://msdn.microsoft.com/en-us/library/765fde44-1f95-4015-80a4-45388f18a42c

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Post #1392884

toddasd

Posted Wednesday, December 05, 2012 7:06 AM

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UPDATE takes only one column. There is no similar 'INSERT' function; UPDATE checks for both.

Your line would change to

IF (UPDATE(Col1) OR UPDATE(Col2) OR UPDATE(Col3))

You could also use COLUMNS_UPDATED, but that may be confusing with the bit mask.

Edit: removed quote

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Post #1392996

Lowell

Posted Wednesday, December 05, 2012 7:12 AM

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I think your trigger model needs to look more like this.
because triggers handle multiple rows in SQL server, you should never declare a variable in a trigger, because it makes you think of one row/one value, instead of the set.
there are exceptions of course, but it's a very good rule of thumb.

also note the UPDATE function doesn't tell you the VALUE changed on a column...only whether the column was included int eh column list for insert/update. so if it was updated to the exisitng value (and a lot of data layers will do that automatically) it's a false detection of a change.

CREATE TRIGGER [TRG_TESTING]
ON TABLE_NAME
AFTER INSERT,UPDATE 
AS
SET NOCOUNT ON

INSERT INTO SomeTrackingTable(ColumnList)
  SELECT ColumnList 
  FROM INSERTED
    LEFT OUTER JOIN DELETED
      ON INSERTED.SomePrimaryKey = DELETED.SomePrimaryKey
  WHERE DELETED.SomePrimaryKey IS NULL --inserted only
     OR (INSERTED.SpecificColumn <> DELETED.SpecificColumn) --this column changed...so we need to log it.

Lowell

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Post #1392999

TheSQLGuru

Posted Thursday, December 06, 2012 6:50 AM

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This can be found in BOL:

1) IF UPDATE(b) OR UPDATE(c) ...

2) IF ( COLUMNS_UPDATED() & 2 = 2 )

Best,

Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru at GMail

Post #1393490

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