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Old January 11th, 2005, 02:08 AM
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Default How to do calculation between 2 tables

I need to minus the dollar amount in Table A from Table B when they meet the criteria. Can T-SQL do this function?

For Example, when Year, MonthID, AcNo and Pid in Table A are the same as those in Table B, the Amt in Table A needs to minus the Amt in Table B.

Table A
Year MonthID AcNo Pid Amt
2002 1 1001 1 2000
2002 1 1001 2 2500
2002 1 1001 3 3000

Table B
Year MonthID AcNo Pid Amt
2002 1 1001 1 200
2002 1 1001 2 500
2002 1 1001 3 30
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Old January 11th, 2005, 04:46 AM
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Though I am not clear with your requirement .. I guess Triggers can be of use to you.

Best Regards

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Old January 13th, 2005, 09:29 PM
Ben Ben is offline
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Rough Guidelines:

For existing data run a query something like:
SET Table1.Amount = Table1.Amount - Table2.Amount
ON Table1.PID = Table2.PID
AND Table1.[Year] = Table2.[Year]
AND Table1.MonthID = Table2.MonthID
AND Table1.AcNo = Table2.AcNo

For future use a Trigger something like:
CREATE Trigger After_IU_Update_T1_From_T2
ON Table2 AFTER Insert,Update
AS IF Update(Amount)
    UPDATE Table1
    SET Table1.Amount = Table1.Amount - inserted.Amount
    FROM Table1 INNER JOIN inserted
    ON Table1.PID = inserted.PID
    AND Table1.[Year] = inserted.[Year]
    AND Table1.MonthID = inserted.MonthID
    AND Table1.AcNo = inserted.AcNo
WHERE inserted.Amount IS NOT NULL

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