What is the difference between WHERE and HAVING?

WHERE and HAVING are both filtering operators in SQL, but they are used at different stages of data processing.

• WHERE filters rows before grouping and aggregation. It applies to individual table records.
• HAVING filters groups obtained after applying aggregate functions (e.g., SUM, COUNT, AVG).

Example:

SELECT department, COUNT(*) AS employee_count
FROM employees
WHERE salary > 50000  -- filter employees with salary greater than 50000
GROUP BY department
HAVING COUNT(*) > 10    -- select departments with more than 10 employees

Here, WHERE filters rows before grouping, and HAVING filters after grouping by departments.