SQL HAVING Clause Explained: Filter Your Data Like a Pro

The only clause that lets you filter based on an aggregate result.

The HAVING clause exists for one specific reason: WHERE cannot filter based on the result of an aggregate function, because aggregates aren't calculated until after grouping happens. HAVING fills that gap.

Basic Syntax

SELECT column, AGG_FUNCTION(column)
FROM table_name
GROUP BY column
HAVING AGG_FUNCTION(column) condition;

Example: Departments With More Than 5 Employees

SELECT department, COUNT(*) AS employee_count
FROM employees
GROUP BY department
HAVING COUNT(*) > 5;

Example: Products With Average Rating Above 4

SELECT product_id, AVG(rating) AS avg_rating
FROM reviews
GROUP BY product_id
HAVING AVG(rating) > 4;

Combining HAVING with Multiple Conditions

SELECT department, AVG(salary) AS avg_salary, COUNT(*) AS total
FROM employees
GROUP BY department
HAVING AVG(salary) > 50000 AND COUNT(*) > 3;

💡 Tip: A quick way to remember the difference: WHERE filters rows before grouping, HAVING filters groups after aggregation.

Common Mistakes to Avoid

Using HAVING without a GROUP BY when a simple WHERE would do
Referencing a column in HAVING that isn't part of GROUP BY or an aggregate
Expecting HAVING to speed up a query — it filters after the aggregation has already been computed