关于MySQL

之前建立的表, 没有填内容却忘记了建立时设置的结构.

使用 

desc <表名>;

查看table的结构, 如下

mysql> desc animal;
+--------------+-------------+------+-----+---------+-------+
| Field        | Type        | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| name         | varchar(20) | YES  |     | NULL    |       |
| weight       | int(11)     | YES  |     | NULL    |       |
| age          | int(11)     | YES  |     | NULL    |       |
| living_place | varchar(20) | YES  |     | NULL    |       |
| color        | int(11)     | YES  |     | NULL    |       |
+--------------+-------------+------+-----+---------+-------+
5 rows in set (0.03 sec)

 

然后发现color项的数据类型建立错了, 需要修改数据类型.

语法:alter table <表名> modify <字段名> <数据类型>

如下:

mysql> alter table animal modify color varchar(20);
Query OK, 1 row affected (0.08 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> desc animal;
+--------------+-------------+------+-----+---------+-------+
| Field        | Type        | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| name         | varchar(20) | YES  |     | NULL    |       |
| weight       | int(11)     | YES  |     | NULL    |       |
| age          | int(11)     | YES  |     | NULL    |       |
| living_place | varchar(20) | YES  |     | NULL    |       |
| color        | varchar(20) | YES  |     | NULL    |       |
+--------------+-------------+------+-----+---------+-------+
5 rows in set (0.01 sec)