How to Efficiently Sum Cash Values by Transaction ID Based on Value Date in SQL?

Calculating Sum with Conditional Value Dates

In a SQL statement, you want to calculate the total cash for each unique transaction ID within the last month. To achieve this, you need to modify an existing statement to include the condition that only cash values with a value date after a specific date should be included.

To address this, you attempted to use the CASE statement, but encountered an error due to incorrect syntax.

The correct syntax for the searched CASE expression is:

CASE
     WHEN Boolean_expression THEN result_expression [ ...n ] 
     [ ELSE else_result_expression ] 
END

The expression should be modified as follows:

SUM(CASE WHEN ValueDate > @startMonthDate THEN cash ELSE 0 END)

This expression evaluates the ValueDate field for each record. If the ValueDate is greater than the specified start month date, the cash value is returned; otherwise, 0 is returned. The resulting values are then summed to provide the total cash for the specified period.

Alternative Approach

For improved performance, consider using a JOIN and GROUP BY statement instead of a dependent subquery:

SELECT SUM(cash)
FROM Table_a AS a
JOIN Table_b AS b ON a.branch = b.branch AND a.transID = b.transID
WHERE ValueDate > @startMonthDate
GROUP BY a.transID

This approach avoids the overhead associated with a subquery and can result in faster execution time.

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