Adding new column after a specific column and defining a default in MySQL?

You need to follow some steps to add a new column after a specific column and defining default value. In order to achieve this, you need to use ALTER command. Let us first create a table −

mysql> create table DemoTable
   (
   StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   StudentFirstName varchar(20),
   StudentAge int,
   StudentCountryName varchar(100)
   );
Query OK, 0 rows affected (0.21 sec)

Let us check the description of table −

mysql> desc DemoTable;

This will produce the following output −

+--------------------+--------------+------+-----+---------+----------------+
| Field              | Type         | Null | Key | Default | Extra          |
+--------------------+--------------+------+-----+---------+----------------+
| StudentId          | int(11)      | NO   | PRI | NULL    | auto_increment |
| StudentFirstName   | varchar(20)  | YES  |     | NULL    |                |
| StudentAge         | int(11)      | YES  |     | NULL    |                |
| StudentCountryName | varchar(100) | YES  |     | NULL    |                |
+--------------------+--------------+------+-----+---------+----------------+
4 rows in set (0.15 sec)

Following is the query to add a new column after a specific column and defining a default. Let us add a new column “StudentLastName” after column name “StudentFirstName”. The default value of StudentLastName column is “Doe”.

mysql> alter table DemoTable add StudentLastName varchar(20) NOT NULL after StudentFirstName;
Query OK, 0 rows affected (0.91 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table DemoTable alter StudentLastName set default 'Doe';
Query OK, 0 rows affected (0.32 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          |
+--------------------+--------------+------+-----+---------+----------------+
| StudentId          | int(11)      | NO   | PRI | NULL    | auto_increment |
| StudentFirstName   | varchar(20)  | YES  |     | NULL    |                |
| StudentLastName    | varchar(20)  | NO   |     | Doe     |                |
| StudentAge         | int(11)      | YES  |     | NULL    |                |
| StudentCountryName | varchar(100) | YES  |     | NULL    |                |
+--------------------+--------------+------+-----+---------+----------------+
5 rows in set (0.01 sec)