Question

Is there a better way to write this query:

    INSERT INTO #Temp (MinDateTime, VehicleID)
    SELECT Min(CAST(RDate AS smalldatetime) + RTime) as MinDateTime, T.VehicleID
    FROM (
        SELECT D.RDate, D.RTime, D.VehicleID
        FROM DELETED AS D 
        JOIN INSERTED AS I ON D.ReceiptID = I.ReceiptID
        AND (D.[RDate] <> I.[RDate] OR D.[RTime] <> I.[RTime] OR D.VehicleID <> I.VehicleID OR D.Liters <> I.Liters OR D.OdometerReading <> I.OdometerReading)
        UNION ALL
        SELECT I.RDate, I.Rtime, I.VehicleID
        FROM INSERTED AS I 
        JOIN DELETED AS D ON I.ReceiptID = D.ReceiptID
        AND (I.[RDate] <> D.[RDate] OR I.[RTime] <> D.[RTime] OR I.VehicleID <> D.VehicleID OR I.Liters <> D.Liters OR I.OdometerReading <> D.OdometerReading)
        UNION ALL
        SELECT D.RDate, D.RTime, D.VehicleID
        FROM DELETED AS D 
        LEFT JOIN INSERTED AS I ON D.ReceiptID = I.ReceiptID
        WHERE I.ReceiptID IS NULL
        UNION ALL
        SELECT I.RDate, I.Rtime, I.VehicleID
        FROM INSERTED AS I 
        LEFT JOIN DELETED AS D ON I.ReceiptID = D.ReceiptID
        WHERE D.ReceiptID IS NULL
    ) AS T
    GROUP BY T.VehicleID
    ORDER BY MinDateTime, T.VehicleID

This is part of an after update trigger that evaluates records who have been deleted/added/inserted and looks at one of the 5 columns if they’ve been modified it generates a list of vehicles and date/time so that the trigger can execute a stored proc that recalculates affected records.

Answer 1

I suspect the inner query could be written as:

    SELECT D.RDate, D.RTime, D.VehicleID
    FROM DELETED D full outer JOIN
         INSERTED I
         ON D.ReceiptID = I.ReceiptID
    where ((D.[RDate] <> I.[RDate] OR D.[RTime] <> I.[RTime] OR D.VehicleID <> I.VehicleID OR D.Liters <> I.Liters OR D.OdometerReading <> I.OdometerReading) or
           (I.[RDate] <> D.[RDate] OR I.[RTime] <> D.[RTime] OR I.VehicleID <> D.VehicleID OR I.Liters <> D.Liters OR I.OdometerReading <> D.OdometerReading) or
         I.ReceiptID IS NULL or
         D.ReceiptID IS NULL
        ) and
        (coalesce(i.ReceiptId, d.receiptId) is not null)  -- check that at least one has a value

In other words, I replaced the sequence of unions with a full outer join and then put all the conditions together in a where clause, separated by ors.