What is the difference between WHERE and HAVING?

WHERE and HAVING are SQL clauses for filtering data, but they are used at different stages:

• WHERE filters rows before grouping. It is used to restrict the initial data.
• HAVING filters groups formed after GROUP BY. It allows setting conditions on aggregate functions.

Example:

SELECT author, COUNT(*) as books_count
FROM books
WHERE price > 100
GROUP BY author
HAVING COUNT(*) > 5;

Here, books with a price greater than 100 are selected first (WHERE), then groups by authors are formed, and only those with more than 5 books are selected (HAVING).