How to alter column type of multiple columns in a single MySQL query?

To alter column type of multiple columns in a single MySQL query, the syntax is as follows −

alter table yourTableName
modify column yourColumnName 1 yourDataType1,
modify column yourColumnName 2 yourDataType2,
.
.
N;

Let us first create a table −

mysql> create table DemoTable
(
   Id varchar(100),
   FirstName text,
   LastName text
);
Query OK, 0 rows affected (0.52 sec)

Let us check the description of table −

mysql> desc DemoTable;

This will produce the following output −

+-----------+--------------+------+-----+---------+-------+
| 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)

Following is the query to alter column type of multiple columns. Here, we have altered the column type of columns Id, FirstName and LastName −

mysql> alter table DemoTable
   modify column Id int,
   modify column FirstName varchar(50),
   modify column LastName varchar(50);
Query OK, 0 rows affected (1.63 sec)
Records: 0 Duplicates: 0 Warnings: 0

Let us check the description of table once again −

mysql> desc DemoTable;

This will produce the following output −

+-----------+-------------+------+-----+---------+-------+
| 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)