SELECT SupplierID, AVG(Price)
FROM Products
GROUP BY SupplierID
SELECT SupplierID, CategoryID, AVG(Price)
FROM Products
GROUP BY SupplierID, CategoryID
SELECT SupplierID, CategoryID, AVG(Price)
FROM Products
GROUP BY SupplierID, CategoryID
HAVING AVG(price) >= 100
WHERE 를 쓰게 되면 100불이상인걸 먼저 거르고 그룹바이로 묶기 때문에 HAVING을 쓴다.
SELECT months * salary AS earnings, COUNT(*)
FROM employee
GROUP BY earnings
ORDER BY earnings DESC
LIMIT 1