我们如何能够在另一个子查询内嵌套一个子查询？

如果一个子查询嵌套在另一个子查询中，则称为嵌套子查询。为使其易于理解，我们在以下数据表中创建了嵌套子查询 -

mysql> Select * from Cars;
+------+--------------+---------+
| ID   | Name         | Price   |
+------+--------------+---------+
|    1 | Nexa         | 750000  |
|    2 | Maruti Swift | 450000  |
|    3 | BMW          | 4450000 |
|    4 | VOLVO        | 2250000 |
|    5 | Alto         | 250000  |
|    6 | Skoda        | 1250000 |
|    7 | Toyota       | 2400000 |
|    8 | Ford         | 1100000 |
+------+--------------+---------+
8 rows in set (0.02 sec)

mysql> Select * from Customers;
+-------------+----------+
| Customer_Id | Name     |
+-------------+----------+
|           1 |    Rahul |
|           2 |  Yashpal |
|           3 |   Gaurav |
|           4 | Virender |
+-------------+----------+
4 rows in set (0.00 sec)

mysql> Select * from Reservations;
+------+-------------+------------+
| ID   | Customer_id | Day        |
+------+-------------+------------+
|    1 |           1 | 2017-12-30 |
|    2 |           2 | 2017-12-28 |
|    3 |           2 | 2017-12-29 |
|    4 |           1 | 2017-12-25 |
|    5 |           3 | 2017-12-26 |
+------+-------------+------------+
5 rows in set (0.00 sec)

下面是一个嵌套子查询 -

mysql> Select * from Customers where customer_id IN (Select Customer_id from reservations where id = (Select id from cars WHERE name = 'BMW'));
+-------------+---------+
| Customer_Id | Name    |
+-------------+---------+
|           2 | Yashpal |
+-------------+---------+
1 row in set (0.00 sec)

更新于：22-Jun-2020

131 阅读

开启你的职业生涯

完成课程，获得认证

立刻开始
广告