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数据库教程在指定位置增加字段
mysql教程> -- 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>