SQL Comments

用註解讓 SQL 更好維護

單行註解常用 --，多行註解常用 /* ... */。當查詢變長或多人協作時，註解能大幅提升可讀性。

Example 1 - Single-line Comment

-- 查詢德國客戶
SELECT CustomerName
FROM Customers
WHERE Country = 'Germany';

Example 2 - Multi-line Comment

/* 統計每個國家的客戶數 */
SELECT Country, COUNT(*)
FROM Customers
GROUP BY Country;

Example 3 - 暫時停用條件

SELECT CustomerName, Country
FROM Customers
WHERE 1 = 1
-- AND Country = 'Germany'
ORDER BY CustomerName;

Example 4 - 為複雜查詢加段落說明

/* Step 1: 先找每位客戶的訂單數 */
SELECT c.CustomerName, COUNT(o.OrderID) AS OrderCount
FROM Customers c
LEFT JOIN Orders o ON c.CustomerID = o.CustomerID
GROUP BY c.CustomerName;