#查看表的结构
mysql> desc score;
+------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+----------------+
| id | int(4) | NO | PRI | NULL | auto_increment |
| name | char(20) | NO | | NULL | |
| score | double(16,2) | YES | | NULL | |
| evaluation | char(20) | YES | | normal | |
+------------+--------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)
#alter对字段操作
#添加字段
mysql> alter table exam_score add other int(4) default 10;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
#修改字段变为另一个字段
mysql> alter table exam_score change other evaluation char(20) default 'normal';
Query OK, 4 rows affected (0.02 sec)
Records: 4 Duplicates: 0 Warnings: 0
#删除字段(即删除字段中的所有数据)
mysql> alter table exam_score drop column other;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
#修改表名
mysql> rename table exam_score to score;
Query OK, 0 rows affected (0.01 sec)