mysql學習筆記（5）修改數據表

1.修改表名：
alter table table_oldname rename [to] table_newname;
mysql> alter table example0 rename user;
Query OK, 0 rows affected (0.00 sec)

2.修改字段數據類型：
alter table table_name modify attribute data_type;
mysql> desc user;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| stu_id   | int(11)     | NO   | PRI | NULL    |       |
| stu_name | varchar(20) | YES  |     | NULL    |       |
| stu_sex  | tinyint(1)  | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> alter table user modify stu_name varchar(30);
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc user;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| stu_id   | int(11)     | NO   | PRI | NULL    |       |
| stu_name | varchar(30) | YES  |     | NULL    |       |
| stu_sex  | tinyint(1)  | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.01 sec)

3.修改字段名：
alter table table_name chane old_attribute new_attribute new_data_type;
mysql> desc user;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| stu_id   | int(11)     | NO   | PRI | NULL    |       |
| stu_name | varchar(30) | YES  |     | NULL    |       |
| stu_sex  | tinyint(1)  | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.01 sec)

mysql> alter table user change stu_name name varchar(30);
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc user;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| stu_id  | int(11)     | NO   | PRI | NULL    |       |
| name    | varchar(30) | YES  |     | NULL    |       |
| stu_sex | tinyint(1)  | YES  |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

增長字段
alter table table_name add attribute_1 data_thype [constraint] [first|after attribute_2]
在不指名位置的狀況下，默認字段增長在最後一列：
mysql> alter table user add age int(4) not null;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc user;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| stu_id  | int(11)     | NO   | PRI | NULL    |       |
| name    | varchar(30) | YES  |     | NULL    |       |
| stu_sex | tinyint(1)  | YES  |     | NULL    |       |
| age     | int(4)      | NO   |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

在表的第一列增長字段：
mysql> alter table user add num int(8)  first;          
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc user;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| num     | int(8)      | YES  |     | NULL    |       |
| stu_id  | int(11)     | NO   | PRI | NULL    |       |
| name    | varchar(30) | YES  |     | NULL    |       |
| stu_sex | tinyint(1)  | YES  |     | NULL    |       |
| age     | int(4)      | NO   |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

在表的指定位置後面增長字段：
mysql> alter table user add address varchar(30) not null after stu_id;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc user;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| num     | int(8)      | YES  |     | NULL    |       |
| stu_id  | int(11)     | NO   | PRI | NULL    |       |
| address | varchar(30) | NO   |     | NULL    |       |
| name    | varchar(30) | YES  |     | NULL    |       |
| stu_sex | tinyint(1)  | YES  |     | NULL    |       |
| age     | int(4)      | NO   |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

刪除字段
alter table table_name drop attribute;
mysql> alter table user drop address;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc user;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| num     | int(8)      | YES  |     | NULL    |       |
| stu_id  | int(11)     | NO   | PRI | NULL    |       |
| name    | varchar(30) | YES  |     | NULL    |       |
| stu_sex | tinyint(1)  | YES  |     | NULL    |       |
| age     | int(4)      | NO   |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

修改字段的排列位置
alter table table_name modify attribute_1 data_type first|after attribute_2

修改字段到第一個位置：
mysql> alter table user modify name varchar(30) first;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql>
mysql> desc user;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| name    | varchar(30) | YES  |     | NULL    |       |
| num     | int(8)      | YES  |     | NULL    |       |
| stu_id  | int(11)     | NO   | PRI | NULL    |       |
| stu_sex | tinyint(1)  | YES  |     | NULL    |       |
| age     | int(4)      | NO   |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

修改字段到指定位置：
mysql> alter table user modify sex boolean after name;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc user;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| name   | varchar(30) | YES  |     | NULL    |       |
| sex    | tinyint(1)  | YES  |     | NULL    |       |
| num    | int(8)      | YES  |     | NULL    |       |
| stu_id | int(11)     | NO   | PRI | NULL    |       |
| age    | int(4)      | NO   |     | NULL    |       |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.01 sec)

更改表的存儲引擎 alter table table_name engine=engine_name;