如何在单个MySQL查询中更改多个列的列类型？
要更改单个MySQL查询中多个列的列类型，语法如下-
alter table yourTableName modify column yourColumnName 1 yourDataType1, modify column yourColumnName 2 yourDataType2, . . N;
让我们首先创建一个表-
create table DemoTable ( Id varchar(100), FirstName text, LastName text );
让我们检查表的描述-
desc DemoTable;
这将产生以下输出-
+-----------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+--------------+------+-----+---------+-------+ | Id | varchar(100) | YES | | NULL | | | FirstName | text | YES | | NULL | | | LastName | text | YES | | NULL | | +-----------+--------------+------+-----+---------+-------+ 3 rows in set (0.09 sec)
以下是更改多个列的列类型的查询。在这里，我们更改了Id，FirstName和LastName列的列类型-
alter table DemoTable modify column Id int, modify column FirstName varchar(50), modify column LastName varchar(50); Records: 0 Duplicates: 0 Warnings: 0
让我们再次检查表的描述-
desc DemoTable;
这将产生以下输出-
+-----------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+-------------+------+-----+---------+-------+ | Id | int(11) | YES | | NULL | | | FirstName | varchar(50) | YES | | NULL | | | LastName | varchar(50) | YES | | NULL | | +-----------+-------------+------+-----+---------+-------+ 3 rows in set (0.00 sec)