Using Aggregate Functions in MySQL WHERE Clause
In MySQL, aggregate functions like SUM(), COUNT(), AVG(), MAX(), and MIN() cannot be used in the WHERE clause. The WHERE clause filters individual rows before any grouping or aggregation occurs, so aggregate functions do not yet have meaningful values at that stage.
Use the HAVING clause to filter based on aggregate function results after grouping.
Example: To select departments with total salary greater than 200000, use:
SELECT department_id, SUM(salary) AS total_salary FROM employees GROUP BY department_id HAVING total_salary > 200000;WHERE clause can still filter individual rows before aggregation, e.g.,
WHERE hire_date >= '2023-01-01'.
In summary, WHERE is for filtering raw rows, while HAVING is for filtering aggregated results. Trying to use aggregates in WHERE will result in an error.