SQL HAVING

HAVING 用在分組後的條件判斷，與 WHERE 的用途不同。它常出現在 KPI、排行榜、門檻式報表。

SELECT Country, COUNT(*) AS CustomerCount
FROM Customers
GROUP BY Country
HAVING COUNT(*) >= 5;

SELECT ShipCountry, AVG(Freight) AS AvgFreight
FROM Orders
GROUP BY ShipCountry
HAVING AVG(Freight) > 40
ORDER BY AvgFreight DESC;

差異： WHERE 篩原始資料列，HAVING 篩聚合後結果。