在“网上书店”数据库查询中使用链接查询和子查询
时间: 2023-07-16 18:17:03 浏览: 185
假设“网上书店”数据库中有两个表:书籍表(books)和订单表(orders),其中书籍表中包含每本书的ID、名称、作者和价格,订单表中包含每个订单的ID、顾客ID和书籍ID。
我们可以使用链接查询和子查询来获取以下信息:
1. 获取每个订单中的书籍名称和价格:
链接查询:
```
SELECT orders.order_id, books.book_name, books.price
FROM orders
INNER JOIN books ON orders.book_id = books.book_id;
```
子查询:
```
SELECT order_id, (SELECT book_name FROM books WHERE book_id = orders.book_id) AS book_name, (SELECT price FROM books WHERE book_id = orders.book_id) AS price
FROM orders;
```
2. 获取每个顾客购买的最贵的书籍:
链接查询:
```
SELECT orders.customer_id, MAX(books.price) AS max_price
FROM orders
INNER JOIN books ON orders.book_id = books.book_id
GROUP BY orders.customer_id;
```
子查询:
```
SELECT customer_id, (SELECT MAX(price) FROM books WHERE book_id IN (SELECT book_id FROM orders WHERE customer_id = o.customer_id)) AS max_price
FROM orders o
GROUP BY customer_id;
```
以上是两个示例,你可以根据具体需求进行修改和扩展。
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