如何使用 LEFT JOIN 创建 MySQL 视图?
mysqlmysqli database更新于 2024/2/27 3:45:00
为了说明如何使用 LEFT JOIN 创建 MySQL 视图，我们使用来自"Customers"和"Resreve"表的以下数据 −
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 reserve; +------+------------+ | ID | Day | +------+------------+ | 1 | 2017-12-30 | | 2 | 2017-12-28 | | 2 | 2017-12-25 | | 1 | 2017-12-24 | | 3 | 2017-12-26 | +------+------------+ 5 rows in set (0.00 sec)
现在，以下查询将使用上述表上的 LEFT JOIN 创建一个名为‘customer_VLeft’的视图，该视图将包含尚未预订任何车辆的客户的姓名。
mysql> Create view customer_Vleft AS SELECT NAME from customers LEFT JOIN RESERVE ON customer_id = id WHERE id IS NULL; Query OK, 0 rows affected (0.13 sec) mysql> Select * from customer_Vleft; +----------+ | NAME | +----------+ | Virender | +----------+ 1 row in set (0.00 sec)
