标签:info salary code join name mysql 关联 命令 MySQL
内连接
inner join,⼜叫内连接的部分,主要是获取两个表中字段匹配关系的表。查询关联字段共同拥有的数据
查询两个表共同拥有的数据(inner join)
mysql> use employees;
Database changed
mysql> select e.first_name,e.last_name,e.gender,s.salary from employees as e inner join salaries as s on e.emp_no=s.emp_no where s.salary <40000 limit 3;
+------------+-----------+--------+--------+
| first_name | last_name | gender | salary |
+------------+-----------+--------+--------+
| Shahaf | Famili | M | 39935 |
| Divier | Reistad | F | 39520 |
| Pradeep | Makrucki | M | 39765 |
+------------+-----------+--------+--------+
3 rows in set (0.01 sec)
左连接
获取左表所有记录,获取左边数据表所有符合要求的字段数据信息
获取左表所有记录(left join)
mysql> use anruo;
Database changed
mysql> select p.name,p.age,p.age,w.company,w.salary from person as p left join work as w on p.code=w.code limit 5;
+---------+------+------+---------+--------+
| name | age | age | company | salary |
+---------+------+------+---------+--------+
| zhangli | 24 | 24 | alibaba | 1000 |
| acd | 23 | 23 | zczczc | 1500 |
+---------+------+------+---------+--------+
2 rows in set (0.01 sec)
三表之间的查询
mysql> select p.name,p.age,p.sex,w.company,w.salary,info.type,info.isSafe from person as p left join work as w on p.code=w.code left join workinfo as info on w.workID=info.workID limit 5;
+---------+------+------+---------+--------+-----------+--------+
| name | age | sex | company | salary | type | isSafe |
+---------+------+------+---------+--------+-----------+--------+
| zhangli | 24 | boy | alibaba | 1000 | Full-time | safe |
| acd | 23 | boy | zczczc | 1500 | NULL | NULL |
+---------+------+------+---------+--------+-----------+--------+
2 rows in set (0.00 sec)
右链接
获取右表所有记录的信息,获取右边数据表所有的数据信息
获取右表所有记录(right join)
mysql> select w.company,w.salary,info.type,info.issafe from work as w right join workinfo as info on w.workID=info.workID;
+---------+--------+-----------+--------+
| company | salary | type | issafe |
+---------+--------+-----------+--------+
| alibaba | 1000 | Full-time | safe |
+---------+--------+-----------+--------+
1 row in set (0.00 sec)
通过子查询,来进行查询
mysql> select * from person where code in (select code from work where code=1001);
+----+------+---------+------+------+
| id | code | name | age | sex |
+----+------+---------+------+------+
| 1 | 1001 | zhangli | 24 | boy |
+----+------+---------+------+------+
1 row in set (0.00 sec)
标签:info,salary,code,join,name,mysql,关联,命令,MySQL 来源: https://www.cnblogs.com/zhang1569440624/p/15981737.html
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