mysql怎么用sql语句修改某个列的数据类型？

alter table b change up up varchar(10);

SQL code

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mysql> desc b; +-------------+-------------+------+-----+---------+----------------+ | Field       | Type        | Null | Key | Default | Extra          | +-------------+-------------+------+-----+---------+----------------+ | id          | int(4)      | NO   | PRI | NULL    | auto_increment | | foreignName | varchar(45) | YES  |     | NULL    |                | | up          | float       | YES  |     | NULL    |                | | down        | float       | YES  |     | NULL    |                | +-------------+-------------+------+-----+---------+----------------+ 4 rows in set (0.02 sec) mysql> alter table b change up up varchar(10); Query OK, 4 rows affected (0.19 sec) Records: 4  Duplicates: 0  Warnings: 0 mysql> desc b; +-------------+-------------+------+-----+---------+----------------+ | Field       | Type        | Null | Key | Default | Extra          | +-------------+-------------+------+-----+---------+----------------+ | id          | int(4)      | NO   | PRI | NULL    | auto_increment | | foreignName | varchar(45) | YES  |     | NULL    |                | | up          | varchar(10) | YES  |     | NULL    |                | | down        | float       | YES  |     | NULL    |                | +-------------+-------------+------+-----+---------+----------------+ 4 rows in set (0.00 sec) mysql>