alter是非常强大的一个功能我们可以利用alter来修改数据表表名字体名及一些其它的操作了，下面一起来看看mysql中alter数据表中增加、删除字段与表名修改的一个例子． 修改删除mysql数据库中的数据内容： [root@hk ~]# /usr/local/mysql/bin/mysql -uroot -p'

alter是非常强大的一个功能我们可以利用alter来修改数据表表名字体名及一些其它的操作了，，下面一起来看看mysql中alter数据表中增加、删除字段与表名修改的一个例子．

修改删除mysql数据库中的数据内容：

[root@hk ~]# /usr/local/mysql/bin/mysql -uroot -p'admin' #进入mysql
mysql> create database gbk default character set gbk collate gbk_chinese_ci; #建立一个名字叫做gbk的数据库
mysql> use gbk
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| gbk |
+--------------------+
mysql> show tables;
Empty set (0.00 sec)
mysql> create table test( #建立一个叫做test的数据表
-> id int(4) not null primary key auto_increment,
-> name char(20) not null
-> );
Query OK, 0 rows affected (0.13 sec)

mysql> show tables;
+---------------+
| Tables_in_gbk |
+---------------+
| test |
+---------------+
1 row in set (0.00 sec)
mysql> insert into test(id,name) values(1,'zy'); #插入部分内容
mysql> insert into test(id,name) values(2,'binghe');
mysql> insert into test(id,name) values(3,'zilong');
mysql> insert into test(id,name) values(4,'feng');
mysql> select * from test; #检索整个test表
+----+--------+
| id | name |
+----+--------+
| 1 | zy |
| 2 | binghe |
| 3 | zilong |
| 4 | feng |
+----+--------+
4 rows in set (0.00 sec)
[root@hk ~]# /usr/local/mysql/bin/mysqldump -uroot -p'admin' -B gbk >/tmp/gbk.sql #备份gbk数据库
mysql> update test set name = 'zy' ; #未定义
mysql> select * from test; #
+----+------+
| id | name |
+----+------+
| 1 | zy |
| 2 | zy |
| 3 | zy |
| 4 | zy |
+----+------+
[root@hk ~]# /usr/local/mysql/bin/mysql -uroot -p'admin' mysql> use gbk
mysql> select * from test;
+----+--------+
| id | name |
+----+--------+
| 1 | zy |
| 2 | binghe |
| 3 | zilong |
| 4 | feng |
+----+--------+
mysql> update test set name = 'yadianna' where id =1;
mysql> select * from test;
+----+----------+
| id | name |
+----+----------+
| 1 | yadianna |
| 2 | binghe |
| 3 | zilong |
| 4 | feng |
+----+----------+
mysql> update test set id = 999 where name ='yadianna';
mysql> select * from test;
+-----+----------+
| id | name |
+-----+----------+
| 2 | binghe |
| 3 | zilong |
| 4 | feng |
| 999 | yadianna |
+-----+----------+
mysql> delete from test where id =999;
mysql> select * from test;
+----+--------+
| id | name |
+----+--------+
| 2 | binghe |
| 3 | zilong |
| 4 | feng |
+----+--------+
mysql> delete from test where id <4; #以条件删除
mysql> truncate table test; #删除all
mysql> select * from test;
Empty set (0.00 sec)

接上上面，修改数据库中表名，表中增加、删除字段。

mysql> use gbk #进入gbk数据库
mysql> desc test;
+-------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+----------------+
| id | int(4) | NO | PRI | NULL | auto_increment |
| name | char(20) | NO | | NULL | |
+-------+----------+------+-----+---------+----------------+
mysql> alter table test add gender char(4); #增加gender
mysql> desc test;
+--------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+----------+------+-----+---------+----------------+
| id | int(4) | NO | PRI | NULL | auto_increment |
| name | char(20) | NO | | NULL | |
| gender | char(4) | YES | | NULL | |
+--------+----------+------+-----+---------+----------------+
mysql> alter table test add age int(4) after name;
mysql> desc test;
+--------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+----------+------+-----+---------+----------------+
| id | int(4) | NO | PRI | NULL | auto_increment |
| name | char(20) | NO | | NULL | |
| age | int(4) | YES | | NULL | |
| gender | char(4) | YES | | NULL | |
+--------+----------+------+-----+---------+----------------+
mysql> show tables;
+---------------+
| Tables_in_gbk |
+---------------+
| test |
+---------------+
mysql> rename table test to hello;
mysql> show tables;
+---------------+
| Tables_in_gbk |
+---------------+
| hello |
+---------------+
mysql> alter table hello rename to world;
mysql> show tables;
+---------------+
| Tables_in_gbk |
+---------------+
| world |
+---------------+
mysql> alter table world drop age;
mysql> desc world;
+--------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+----------+------+-----+---------+----------------+
| id | int(4) | NO | PRI | NULL | auto_increment |
| name | char(20) | NO | | NULL | |
| gender | char(4) | YES | | NULL | |
+--------+----------+------+-----+---------+----------------+
3 rows in set (0.00 sec)