MySQL数据库在指定位置增加字段

核心提示： Records: 0 Duplicates: 0 Warnings: 0 mysql> desc t; +-+-+--+-+-+---+ | Field | Type | Null | Key | Default | Extra | +-+-+--+-+-+---+ | id | i

Records: 0 Duplicates: 0 Warnings: 0

mysql> desc t;

+---------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+---------+-------------+------+-----+---------+-------+

| id | int(11) | YES | | NULL | |

| age | int(11) | YES | | NULL | |

| name | varchar(20) | YES | | NULL | |

| address | varchar(50) | YES | | NULL | |

+---------+-------------+------+-----+---------+-------+

4 rows in set (0.00 sec)

mysql>

mysql> -- 测试数据库在指定位置增加字段

mysql> drop table if exists t;

Query OK, 0 rows affected (0.06 sec)

mysql> create table t(age int,address varchar(50));

Query OK, 0 rows affected (0.06 sec)

mysql> desc t;

+---------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+---------+-------------+------+-----+---------+-------+

| age | int(11) | YES | | NULL | |

| address | varchar(50) | YES | | NULL | |

+---------+-------------+------+-----+---------+-------+

2 rows in set (0.02 sec)

mysql> alter table t add column name varchar(20) after age;

Query OK, 0 rows affected (0.16 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> desc t;

+---------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+---------+-------------+------+-----+---------+-------+

| age | int(11) | YES | | NULL | |

| name | varchar(20) | YES | | NULL | |

| address | varchar(50) | YES | | NULL | |

+---------+-------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

mysql> alter table t add column id int FIRST;

Query OK, 0 rows affected (0.13 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> desc t;

+---------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+---------+-------------+------+-----+---------+-------+

| id | int(11) | YES | | NULL | |

| age | int(11) | YES | | NULL | |

| name | varchar(20) | YES | | NULL | |

| address | varchar(50) | YES | | NULL | |

+---------+-------------+------+-----+---------+-------+

4 rows in set (0.00 sec)

mysql>

相关的语法描述为

ALTER [ONLINE | OFFLINE] [IGNORE] TABLE tbl_name alter_specification [, alter_specification] ...alter_specification: table_option ... | ADD [COLUMN] col_name column_definition [FIRST | AFTER col_name ]