SQL HAVING Clause Tutorial

The HAVING clause in SQL is used to filter records after the GROUP BY clause has been applied. It is often used with aggregate functions like COUNT, SUM, AVG, MIN, and MAX to filter groups based on a condition.

Syntax

SELECT column1, aggregate_function(column2)
FROM table_name
GROUP BY column1
HAVING condition;

Example

SELECT department, COUNT(employee_id) AS num_employees
FROM employees
GROUP BY department
HAVING COUNT(employee_id) > 10;

In this example, the query returns departments with more than 10 employees.

Key Points

• HAVING is used after GROUP BY.
• It filters groups based on aggregate conditions.
• Unlike WHERE, which filters rows before grouping, HAVING filters after grouping.

Common Mistakes

• Using HAVING without GROUP BY.
• Confusing HAVING with WHERE.

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