SQL Server 2008 : update multiple columns in trigger - sql

Question

Maybe my original post was little messy, so I didn't get much help. I updated my trigger with the AuditTest table.... Please see if you can help.
I am very new to triggers and trying to put together an audit table where it tracks the value changes on certain columns.
I have a lot of columns like: Qty, UnitSell, Discount, ProductName ...etc. This code below seems to work, which detects the Qty or UnitSell value changes, then do the INSERT INTO the audit table (now I just named it as TEST1)
If I would keep repeating the IF UPDATE(FieldName) statement for other columns, I think it will work, but it is too cumbersome in which keep repeating the same codes.
Is that way to optimize this, so I don't have to repeating the same IF UPDATE (Fieldname) statement?
alter TRIGGER trigger_Test_AfterUpdate
ON [dbo].ERP_QuoteDetail
FOR UPDATE
AS
declare #QuoteDetailID int;
select #QuoteDetailID = i.QuoteDetailID from inserted i;
--- Updating QTY if old/new value change
DECLARE #iQty int; SELECT #iQty = i.Qty from inserted i;
DECLARE #dQty int; SELECT #dQty = d.Qty from deleted d;
if update(QTY) and exists (select * from deleted d WHERE Qty <> #iQty)
BEGIN
-- Insert into the audit table
insert into AuditTest (
[Type]
,[TableName]
,[PKCol]
,[PK]
,[FieldName]
,[OldValue]
,[NewValue]
,[UpdateDate]
,[DBUsername]
,[UserID]
)
values('u'
, 'Table_QuoteDetail'
, 'QuoteDetail'
, #QuoteDetailID
, 'QTY'
, #dQty
, #iQty
, GETDATE()
, '123'
, '456'
);
PRINT 'AFTER UPDATE Trigger fired.'
END
--- Updating QTY if old/new value change
DECLARE #iUnitSell int; SELECT #iUnitSell = i.UnitSell from inserted i;
DECLARE #dUnitSell int; SELECT #dUnitSell = d.Qty from deleted d;
if update(UnitSell) and exists (select * from deleted d
WHERE UnitSell <> #iUnitSell )
BEGIN
-- Insert into the audit table
insert into AuditTest (
[Type]
,[TableName]
,[PKCol]
,[PK]
,[FieldName]
,[OldValue]
,[NewValue]
,[UpdateDate]
,[DBUsername]
,[UserID]
)
values('u'
, 'Table_QuoteDetail'
, 'QuoteDetail'
, #QuoteDetailID
, 'UnitSell'
, #dUnitSell
, #iUnitSell
, GETDATE()
, '123'
, '456'
);
PRINT 'AFTER UPDATE Trigger fired.'
END
GO

Answer 1

You can consider using the Change Data Capture feature of SQL Server for auditing. CDC stores a record of all inserted, updated and deleted rows for whichever tables have CDC enabled. This will effectively replace the need for triggers in your case.
Details on how to enable and configure CDC can be found here.

Answer 2

Your fundamental flaw is that you seem to expect the trigger to be fired once per row - this is NOT the case in SQL Server. Instead, the trigger fires once per statement, and the pseudo table Deleted might contain multiple rows.
Given that that table might contain multiple rows - which one do you expect will be selected here??
select #QuoteDetailID = i.QuoteDetailID from inserted i;
It's undefined - you might get the values from arbitrary rows in Inserted.
You need to rewrite your entire trigger with the knowledge that the Inserted and Deleted pseudo tables WILL contain multiple rows. You need to work with set-based operations - don't expect just a single row in Deleted or Inserted !