В чем различия между операторами WHERE и HAVING в SQL?

WHERE filters rows before grouping (GROUP BY), while HAVING filters groups after grouping. WHERE can use columns that are not in SELECT, HAVING usually uses aggregate functions or columns present in GROUP BY.

Example:

SELECT
    category,
    COUNT(*) as total_items
FROM
    products
WHERE
    price > 10 // Filter products before grouping by category
GROUP BY
    category
HAVING
    COUNT(*) > 5; // Filter category groups with more than 5 products

Comparison:

Operator	Purpose	Applies to	Can use aggregate functions	Execution order relative to GROUP BY
WHERE	Row filtering	Individual rows	No	Before
HAVING	Group filtering	Groups of rows	Yes	After