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MySQL数据库在指定位置增加字段
作者：佚名 责任编辑：admin 更新时间：2022-06-22
MySQL数据库在指定位置增加字段：
本身属于MySQL的基本语法，这里给出一个例子。
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 ]
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