MySQL利用update实现多表更新
一、数据准备
创建stu（学生）表和certificate（证书）表，并输入数据，代码如下：
create table stu(stu_id int primary key,
stu_name char(20) not null default '',
certificate_no char(20) not null default ''
);
insert into stu(stu_id,stu_name) values(10001,'张晓云'),(10002,'王云飞'),
(10003,'李大鹏'),(10004,'王大刚'),(10005,'张小倩'),(10006,'刘明明'),
(10007,'刘涛'),(10008,'张华'),(10009,'陈冰'),(10010,'张静静');
create table certificate(stu_id int primary key,
certificate_type char(50) not null default '',
certificate_no char(20) not null default '',
certificate_date datetime
);
insert into certificate(stu_id,certificate_type,certificate_no,certificate_date)
values(10001,'计算机二级office高级应用','Comp-2-25879','2018-3-15'),
(10002,'计算机三级网络技术','Comp-3-25666','2018-9-28'),
(10003,'英语四级','CET-4-12458','2018-12-25'),
(10005,'英语四级','CET-4-25487','2018-12-25'),
(10007,'英语六级','CET-6-42156','2019-6-28'),
(10008,'英语六级','CET-6-37455','2019-6-28');
如果stu表的学生考取的有证书，则把certificate表中的certificate_no填入stu表。
二、使用join关键字建立连接
mysql> update stu s inner join certificate c on s.stu_id=c.stu_id
set s.certificate_no=c.certificate_no;
Query OK, 6 rows affected (0.01 sec)
Rows matched: 6 Changed: 6 Warnings: 0
mysql> select * from stu;
+--------+-----------+----------------+
| stu_id | stu_name | certificate_no |
+--------+-----------+----------------+
| 10001 | 张晓云 | Comp-2-25879 |
| 10002 | 王云飞 | Comp-3-25666 |
| 10003 | 李大鹏 | CET-4-12458 |
| 10004 | 王大刚 | |
| 10005 | 张小倩 | CET-4-25487 |
| 10006 | 刘明明 | |
| 10007 | 刘涛 | CET-6-42156 |
| 10008 | 张华 | CET-6-37455 |
| 10009 | 陈冰 | |
| 10010 | 张静静 | |
+--------+-----------+----------------+
10 rows in set (0.00 sec)
三、不使用join关键字建立连接
mysql> update stu set certificate_no='';
Query OK, 6 rows affected (0.01 sec)
Rows matched: 10 Changed: 6 Warnings: 0
mysql> select * from stu;
+--------+-----------+----------------+
| stu_id | stu_name | certificate_no |
+--------+-----------+----------------+
| 10001 | 张晓云 | |
| 10002 | 王云飞 | |
| 10003 | 李大鹏 | |
| 10004 | 王大刚 | |
| 10005 | 张小倩 | |
| 10006 | 刘明明 | |
| 10007 | 刘涛 | |
| 10008 | 张华 | |
| 10009 | 陈冰 | |
| 10010 | 张静静 | |
+--------+-----------+----------------+
10 rows in set (0.01 sec)
mysql> update stu s,certificate c
set s.certificate_no=c.certificate_no
where s.stu_id=c.stu_id;
Query OK, 6 rows affected (0.01 sec)
Rows matched: 6 Changed: 6 Warnings: 0
mysql> select * from stu;
+--------+-----------+----------------+
| stu_id | stu_name | certificate_no |
+--------+-----------+----------------+
| 10001 | 张晓云 | Comp-2-25879 |
| 10002 | 王云飞 | Comp-3-25666 |
| 10003 | 李大鹏 | CET-4-12458 |
| 10004 | 王大刚 | |
| 10005 | 张小倩 | CET-4-25487 |
| 10006 | 刘明明 | |
| 10007 | 刘涛 | CET-6-42156 |
| 10008 | 张华 | CET-6-37455 |
| 10009 | 陈冰 | |
| 10010 | 张静静 | |
+--------+-----------+----------------+
10 rows in set (0.00 sec)
四、使用子查询
mysql> update stu set certificate_no='';
Query OK, 4 rows affected (0.00 sec)
Rows matched: 6 Changed: 4 Warnings: 0
mysql> select * from stu;
+--------+-----------+----------------+
| stu_id | stu_name | certificate_no |
+--------+-----------+----------------+
| 10001 | 张晓云 | |
| 10002 | 王云飞 | |
| 10003 | 李大鹏 | |
| 10004 | 王大刚 | |
| 10005 | 张小倩 | |
| 10006 | 刘明明 | |
| 10007 | 刘涛 | |
| 10008 | 张华 | |
| 10009 | 陈冰 | |
| 10010 | 张静静 | |
+--------+-----------+----------------+
10 rows in set (0.01 sec)
mysql> update stu set stu.certificate_no=
(select certificate.certificate_no from certificate where certificate.stu_id=stu.stu_id)
where exists (select 1 from certificate where certificate.stu_id=stu.stu_id);
Query OK, 0 rows affected (0.01 sec)
Rows matched: 6 Changed: 0 Warnings: 0
mysql> select * from stu;
+--------+-----------+----------------+
| stu_id | stu_name | certificate_no |
+--------+-----------+----------------+
| 10001 | 张晓云 | Comp-2-25879 |
| 10002 | 王云飞 | Comp-3-25666 |
| 10003 | 李大鹏 | CET-4-12458 |
| 10004 | 王大刚 | |
| 10005 | 张小倩 | CET-4-25487 |
| 10006 | 刘明明 | |
| 10007 | 刘涛 | CET-6-42156 |
| 10008 | 张华 | CET-6-37455 |
| 10009 | 陈冰 | |
| 10010 | 张静静 | |
+--------+-----------+----------------+
10 rows in set (0.00 sec)
五、同时更新两个表中的数据
mysql> update stu set certificate_no='';
Query OK, 6 rows affected (0.01 sec)
Rows matched: 10 Changed: 6 Warnings: 0
mysql> select * from stu;
+--------+-----------+----------------+
| stu_id | stu_name | certificate_no |
+--------+-----------+----------------+
| 10001 | 张晓云 | |
| 10002 | 王云飞 | |
| 10003 | 李大鹏 | |
| 10004 | 王大刚 | |
| 10005 | 张小倩 | |
| 10006 | 刘明明 | |
| 10007 | 刘涛 | |
| 10008 | 张华 | |
| 10009 | 陈冰 | |
| 10010 | 张静静 | |
+--------+-----------+----------------+
10 rows in set (0.01 sec)
mysql> update stu s inner join certificate c on s.stu_id=c.stu_id
set s.certificate_no=c.certificate_no, c.certificate_date='2019-8-8'
where certificate_type='英语六级';
Query OK, 4 rows affected (0.01 sec)
Rows matched: 4 Changed: 4 Warnings: 0
mysql> select * from stu;
+--------+-----------+----------------+
| stu_id | stu_name | certificate_no |
+--------+-----------+----------------+
| 10001 | 张晓云 | |
| 10002 | 王云飞 | |
| 10003 | 李大鹏 | |
| 10004 | 王大刚 | |
| 10005 | 张小倩 | |
| 10006 | 刘明明 | |
| 10007 | 刘涛 | CET-6-42156 |
| 10008 | 张华 | CET-6-37455 |
| 10009 | 陈冰 | |
| 10010 | 张静静 | |
+--------+-----------+----------------+
10 rows in set (0.00 sec)
mysql> select * from certificate;
+--------+-----------------------------------+----------------+---------------------+
| stu_id | certificate_type | certificate_no | certificate_date |
+--------+-----------------------------------+----------------+---------------------+
| 10001 | 计算机二级office高级应用 | Comp-2-25879 | 2018-03-15 00:00:00 |
| 10002 | 计算机三级网络技术 | Comp-3-25666 | 2018-09-28 00:00:00 |
| 10003 | 英语四级 | CET-4-12458 | 2018-12-25 00:00:00 |
| 10005 | 英语四级 | CET-4-25487 | 2018-12-25 00:00:00 |
| 10007 | 英语六级 | CET-6-42156 | 2019-08-08 00:00:00 |
| 10008 | 英语六级 | CET-6-37455 | 2019-08-08 00:00:00 |
+--------+-----------------------------------+----------------+---------------------+
6 rows in set (0.00 sec)
