MySQL數據庫在指定位置增加字段

 　　MySQL數據庫在指定位置增加字段：

　　本身屬於MySQL的基本語法，這裡給出一個例子。

　　mysql> -- 測試數據庫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>

　　相關的語法描述為

　　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 ]