Explain the difference between WHERE and HAVING

WHERE and HAVING are filtering conditions in SQL, but they are applied at different stages of data processing.

• WHERE filters rows before grouping. It limits the dataset that will be included in aggregate functions.
• HAVING filters groups after applying aggregate functions (e.g., SUM, COUNT).

Example:

SELECT department, COUNT(*) as emp_count
FROM employees
WHERE salary > 50000  -- filter employees with salary above 50000
GROUP BY department
HAVING COUNT(*) > 10;    -- select departments with more than 10 employees

Thus, WHERE works with individual rows, while HAVING works with aggregated groups.