mysql 数据操作 多表查询 多表连接查询 内连接

内连接：只连接匹配的行

只取两张表共同的部分,相当于利用where 过滤条件从笛卡尔积结果中筛选出了正确的结果

select * from 左表 inner join 要连接的表 on 条件

#department没有204这个部门，因而employee表中关于204这条员工信息没有匹配出来

mysql> select * from employee inner join department on employee.dep_id = department.id;
+----+-----------+--------+------+--------+------+--------------+
| id | name      | sex    | age  | dep_id | id   | name         |
+----+-----------+--------+------+--------+------+--------------+
|  1 | mike      | male   |   18 |    200 |  200 | 技术         |
|  2 | alex      | female |   48 |    201 |  201 | 人力资源     |
|  3 | jack      | male   |   38 |    201 |  201 | 人力资源     |
|  4 | yuanhao   | female |   28 |    202 |  202 | 销售         |
|  5 | liwenzhou | male   |   18 |    200 |  200 | 技术         |
+----+-----------+--------+------+--------+------+--------------+
5 rows in set (0.01 sec)

select * from employee inner join department on employee.dep_id = department.id where

后面也可以加上where 过滤条件