How Can I Use the SUM() Function for Comparisons in a MySQL WHERE Clause?

Using MySQL SUM() Function in a WHERE Clause

In MySQL, using the SUM() function in a WHERE clause directly is limited. Instead, you can use the HAVING clause in conjunction with the SUM() function.

WHERE SUM(cash) > 500 Issue:
The provided query using WHERE SUM(cash) > 500 will not work because aggregate functions like SUM() cannot be used for comparison in a WHERE clause.

HAVING Clause:
To use aggregate functions for comparison, you need to use the HAVING clause. The HAVING clause is used with the GROUP BY clause to constrain the grouping results.

Example Query:
To find the first row where the running total of cash exceeds 500:

<code class="sql">SELECT y.id, y.cash
FROM (SELECT t.id,
               t.cash,
               (SELECT SUM(x.cash)
                  FROM table x
                 WHERE x.id <= t.id) AS running_total
         FROM table t
     ORDER BY t.id) y
WHERE y.running_total > 500
ORDER BY y.id
LIMIT 1;</code>

Explanation:

• The subquery derives the running total for each row.
• The column alias for the running total can be referenced in the WHERE clause.
• The query is ordered by ID and limited to the first row to retrieve the desired result.

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