SQL Aliases

可用 AS 為欄位或表格命名別名，讓結果或 JOIN 語法更清楚。當查詢越長，別名的重要性越高。

SELECT CustomerName AS 客戶名稱,
       Country AS 國家
FROM Customers;

SELECT c.CustomerName, o.OrderID
FROM Customers AS c
JOIN Orders AS o ON c.CustomerID = o.CustomerID;

SELECT Country,
       COUNT(*) AS CustomerCount
FROM Customers
GROUP BY Country;

SELECT ProductName,
       CASE WHEN Price >= 100 THEN 'Premium' ELSE 'Standard' END AS ProductTier
FROM Products;