MySQL数据库应用（10）DML之修改表中的记录

一、修改表中数据

　　　　1、修改表中指定条件固定列的数据

　　　　　　　　1）命令语法：update  表名  set  字段=新值，…where 条件（一定要注意条件）

　　　　　　　　2）修改指定的行字段内容

　　　　　　　　　　a.查看要修改的表

mysql> select * from test;
+----+---------+
| id | name    |
+----+---------+
|  3 | inca    |
|  5 | kaka    |
|  1 | oldboy  |
|  2 | oldgirl |
|  4 | zuma    |
+----+---------+
5 rows in set (0.00 sec)

 　　　　　　　　　　b.修改id为3的行的名字为gongli。

mysql> update test set name='gongli' where id=3;
Query OK, 1 row affected (0.38 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from test;
+----+---------+
| id | name    |
+----+---------+
|  3 | gongli  |
|  5 | kaka    |
|  1 | oldboy  |
|  2 | oldgirl |
|  4 | zuma    |
+----+---------+
5 rows in set (0.00 sec)

　　　　2、修改表中所有行的数据

　　　　　　　　3）严重的案例（可能误操作导致数据对视）

　　　　　　　　　　a.不带条件更改所有表的记录

mysql> update test set name='gongli';  <==如果不加条件要十分小心。专业做法，一定要多问开发确定，如果你发给开发的语句要括号注明，防治DBA误会。
Query OK, 4 rows affected (0.00 sec)
Rows matched: 5  Changed: 4  Warnings: 0

　　　　　　　　　　b.更改了所有的记录

mysql> select * from test;
+----+--------+
| id | name   |
+----+--------+
|  1 | gongli |
|  2 | gongli |
|  3 | gongli |
|  4 | gongli |
|  5 | gongli |
+----+--------+
5 rows in set (0.00 sec)

　　　　　　　　　　c.数据恢复

[root@localhost ~]# mysql -uroot -pdubin oldboy </opt/oldboy_bak.sql
[root@localhost ~]# 
[root@localhost ~]# 
[root@localhost ~]# mysql -uroot -pdubin
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 6
Server version: 5.5.32 Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> use oldboy
Database changed
mysql> select * from test;
+----+---------+
| id | name    |
+----+---------+
|  1 | oldboy  |
|  2 | oldgirl |
|  3 | inca    |
|  4 | zuma    |
|  5 | kaka    |
+----+---------+
5 rows in set (0.00 sec)

mysql> 

 　　　　3、防止误操作MySQL数据库一例

[root@localhost data]# mysql -uroot -pdubin -U
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 10
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> select * from test;
ERROR 1046 (3D000): No database selected
mysql> use oldboy
Database changed
mysql> select * from test;
+----+-----------+
| id | name      |
+----+-----------+
|  1 | oldboy    |
|  2 | oldgirl   |
|  3 | inca      |
|  4 | zuma      |
|  5 | kaka      |
|  6 | xiaozhang |
+----+-----------+
6 rows in set (0.00 sec)

mysql> update test set name='gongli';
ERROR 1175 (HY000): You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
mysql> quit
Bye
[root@localhost data]# alias mysql='mysql -U'
[root@localhost data]# mysql -uroot -pdubin 
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 11
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> use oldboy
Database changed
mysql> select * from test;
+----+-----------+
| id | name      |
+----+-----------+
|  1 | oldboy    |
|  2 | oldgirl   |
|  3 | inca      |
|  4 | zuma      |
|  5 | kaka      |
|  6 | xiaozhang |
+----+-----------+
6 rows in set (0.00 sec)

mysql> update test set name='gongli';
ERROR 1175 (HY000): You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
mysql>