What is the difference between WHERE and HAVING in SQL?

In SQL, WHERE and HAVING are used for filtering, but at different stages of data processing:

• WHERE filters rows before grouping (before GROUP BY). It applies to individual table records.
• HAVING filters already grouped data, meaning it is applied after GROUP BY and allows filtering of aggregated values.

Example:

SELECT department, COUNT(*) AS employee_count
FROM employees
WHERE salary > 50000  -- filter employees with salary above 50k
GROUP BY department
HAVING COUNT(*) > 10      -- select departments with more than 10 employees

Here, WHERE selects rows with salary above 50,000, and HAVING filters groups of departments with more than 10 employees.