Mis vahe on SQL-is WHERE ja HAVING lausetel?

WHERE applies before grouping and filters the rows of the FROM result. HAVING applies after grouping and filters the groups formed with GROUP BY.

Example:

Suppose we have a table orders with columns customer_id, order_date, and amount.

Find all customers whose total order amount exceeds 1000:

SELECT customer_id, SUM(amount)
FROM orders
GROUP BY customer_id
HAVING SUM(amount) > 1000;

Find all orders with an amount greater than 1000:

SELECT customer_id, order_date, amount
FROM orders
WHERE amount > 1000;

Comparison table:

Feature	WHERE	HAVING
Application	On individual rows before grouping	On groups of rows after grouping
Uses	Columns from FROM	Aggregate functions and columns from GROUP BY
Executed	Before GROUP BY	After GROUP BY
Aggregate functions	Cannot be used directly	Can be used