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Trigger not always firing?

I have the following trigger in my SQL 2000 database:

CREATE TRIGGER dbo.tgrServiceDetail
ON dbo.tblServiceDetail
FOR INSERT, UPDATE, DELETE
AS
      SET NOCOUNT ON
      UPDATE S SET
            TotalAmount = ISNULL(TotalAmount,0)
              + (ISNULL(I.SumOfAmount,0)
              - ISNULL(D.SumOfAmount,0)),
            TotalRewardBase = ISNULL(TotalRewardBase,0)
              + (ISNULL(I.SumOfRewardAmount,0)
              - ISNULL(D.SumOfRewardAmount,0)),
            TaxableTotal1 = ISNULL(TaxableTotal1,0)
              + (ISNULL(I.SumTaxableAmount1,0)
              - ISNULL(D.SumTaxableAmount1,0)),
            TaxableTotal2 = ISNULL(TaxableTotal2,0)
              + (ISNULL(I.SumTaxableAmount2,0)
              - ISNULL(D.SumTaxableAmount2,0))
      FROM tblService as S
            LEFT JOIN
                  (SELECT ServiceID,
                         SUM(Amount) As SumOfAmount,
                         SUM(RewardAmount) As SumOfRewardAmount,
                         SUM(TaxableAmount1) as SumTaxableAmount1,
                         SUM(TaxableAmount2) as SumTaxableAmount2
                   FROM inserted
                   GROUP BY ServiceID) AS I
            ON S.ServiceID = I.ServiceID
            LEFT JOIN
                  (SELECT ServiceID,
                         SUM(Amount) As SumOfAmount,
                         SUM(RewardAmount) As SumOfRewardAmount,
                         SUM(TaxableAmount1) as SumTaxableAmount1,
                         SUM(TaxableAmount2) as SumTaxableAmount2
                   FROM deleted
                   GROUP BY ServiceID) AS D
              ON S.ServiceID = D.ServiceID
      SET NOCOUNT OFF

I am using an Access Data Project as a front end. I set up triggers so that I wouldn't have to mess with computations everywhere something changes on any of my forms.
Now, to my horror, it appears that my trigger is often not firing the very first time I add detail records to my ServiceDetail table.

Once the trigger successfully fires once, then it always seems to work. However, it gets out of sync with the table that first time, so it is then always out of sync.

I have two questions:

1. Why does this happen? I was led to believe that triggers ALWAYS fire when a table is changed.

2. How can I set this up to recompute the values in the detail table by summing them again from scratch instead of computing the incremental change. I created this trigger by cloning some other stuff I saw, so I am not an expert at triggers by any means.

Any help would be appreciated.

Hilaire

You could write it as follows to keep things in synch.
Any particular reason to set NOCOUNT ON in the trigger ? I always do it in stored procedures intended to work with ADO, but never used it in a trigger ?

Although I understand the logic behind your code above, to calculate only the delta after each and every operation on the table, I think the code below should be more robust.

Putting the where clause
WHERE ServiceID in (SELECT ServiceID FROM inserted UNION SELECT ServiceID FROM deleted)
in the inner query should make things faster then in the outer query.

CREATE TRIGGER dbo.tgrServiceDetail
ON dbo.tblServiceDetail
FOR INSERT, UPDATE, DELETE
AS
UPDATE S SET
TotalAmount = b.TotalAmount,
TotalRewardBase = b.TotalRewardBase,
TaxableTotal1 = b.TaxableTotal1,
TaxableTotal2 = b.TaxableTotal2
FROM tblService as S
INNER JOIN (
SELECT ServiceID,
SUM(Amount) As SumOfAmount,
SUM(RewardAmount) As SumOfRewardAmount,
SUM(TaxableAmount1) as SumTaxableAmount1,
SUM(TaxableAmount2) as SumTaxableAmount2
FROM dbo.tblServiceDetail
WHERE ServiceID in (SELECT ServiceID FROM inserted UNION SELECT ServiceID FROM deleted)
GROUP BY ServiceID
) AS b ON S.ServiceID = I.ServiceID

Hilaire

Oops wrong alias name

CREATE TRIGGER dbo.tgrServiceDetail
ON dbo.tblServiceDetail
FOR INSERT, UPDATE, DELETE
AS
UPDATE S SET
TotalAmount = b.TotalAmount,
TotalRewardBase = b.TotalRewardBase,
TaxableTotal1 = b.TaxableTotal1,
TaxableTotal2 = b.TaxableTotal2
FROM tblService as S
INNER JOIN (
SELECT ServiceID,
SUM(Amount) As SumOfAmount,
SUM(RewardAmount) As SumOfRewardAmount,
SUM(TaxableAmount1) as SumTaxableAmount1,
SUM(TaxableAmount2) as SumTaxableAmount2
FROM dbo.tblServiceDetail
WHERE ServiceID in (SELECT ServiceID FROM inserted UNION SELECT ServiceID FROM deleted)
GROUP BY ServiceID
) AS b ON S.ServiceID = b.ServiceID

ASKER CERTIFIED SOLUTION

Hilaire

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Lowfatspread

not sure why you have problems with the first insert...

but this is more like how i'd write it..

CREATE TRIGGER dbo.tgrServiceDetail
ON dbo.tblServiceDetail
FOR INSERT, UPDATE, DELETE
AS

UPDATE tblService SET
TotalAmount = Coalesce(TotalAmount,0)
+ Coalesce(Y.Amount,0)
, TotalRewardBase = Coalesce(TotalRewardBase,0)
+ Coalesce(Y.RewardAmount,0)
, TaxableTotal1 = Coalesce(TaxableTotal1,0)
+ Coalesce(Y.TaxableAmount1,0)
, TaxableTotal2 = Coalesce(TaxableTotal2,0)
+ Coalesce(Y.TaxableAmount2,0)

FROM tblService as S
Inner Join (Select Serviceid
,Sum(amount) as amount
,sum(RewardAmount) as RewardAmount
,Sum(Taxableamount1) as Taxableamount1
,Sum(Taxableamount2) as Taxableamount2
From (
SELECT coalesce(i.ServiceID,d.serviceid) as serviceid,
coalesce(I.Amount,0) - coalesce(D.amount,0) As Amount,
coalesce(I.RewardAmount,0) - coalesce(D.RewardAmount,0) As RewardAmount,
coalesce(I.TaxableAmount1,0) - coalesce(D.TaxableAmount1,0) as TaxableAmount1,
coalesce(I.TaxableAmount2,0) - coalesce(D.TaxableAmount2,0) as TaxableAmount2
FROM inserted
Full Outer Join Deleted
on I.serviceid=d.serviceid
) as X
GROUP BY ServiceID
Having Sum(amount) <> 0 or Sum(RewardAmount) <> 0
or Sum(Taxableamount1) <> 0 or sum(Taxableamount2) <> 0
) AS Y
ON S.ServiceID = Y.ServiceID

tk3

ASKER

Hilare,
Your answer was fantastic!