【LeetCode】183. 從不訂購的客戶
題目
某網站包含兩個表，Customers 表和 Orders 表。編寫一個 SQL 查詢，找出所有從不訂購任何東西的客戶。
Customers 表：
| Id | Name |
|---|---|
| 1 | Joe |
| 2 | Henry |
| 3 | Sam |
| 4 | Max |
Orders 表：
| Id | CustomerId |
|---|---|
| 1 | 3 |
| 2 | 1 |
例如給定上述表格，你的查詢應返回：
| Customers |
|---|
| Henry |
| Max |
分析解讀
本題考察的知識點是兩表關聯查詢，但是需要注意的是篩選條件為二者不匹配的情況。這裡可以考慮使用not in來解決。要注意Customers表的Id是和Orders
CustomerId欄位相對應的。
我的答案：
select Name as Customers from Customers
where Id not in (select CustomerId from Orders);
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