41 lines
689 B
Markdown
41 lines
689 B
Markdown
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## 题目
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某网站包含两个表，Customers 表和 Orders 表。编写一个 SQL 查询，找出所有从不订购任何东西的客户。
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Customers 表：
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```
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+----+-------+
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| Id | Name |
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+----+-------+
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| 1 | Joe |
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| 2 | Henry |
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| 3 | Sam |
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| 4 | Max |
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+----+-------+
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```
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Orders 表：
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```
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+----+------------+
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| Id | CustomerId |
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+----+------------+
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| 1 | 3 |
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| 2 | 1 |
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+----+------------+
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```
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例如给定上述表格，你的查询应返回：
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```
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+-----------+
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| Customers |
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+-----------+
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| Henry |
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| Max |
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+-----------+
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```
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## 答案
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```sql
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select Name as Customers
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from Customers a
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where a.id not in (select CustomerId from Orders)
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```
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