В чем разница между предложениями WHERE и HAVING в SQL?

WHERE is applied before grouping and filters the result rows of FROM. HAVING is applied 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 orders exceed 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	To individual rows before grouping	To 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