Inserting data into a new column of an already existing table in MySQL?

Let us first create a table −

mysql> create table DemoTable(
   Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   Name varchar(100)
);
Query OK, 0 rows affected (0.47 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable(Name) values('John');
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable(Name) values('Bob');
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable(Name) values('Adam');
Query OK, 1 row affected (0.28 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+----+------+
| Id | Name |
+----+------+
| 1 | John  |
| 2 | Bob   |
| 3 | Adam  |
+----+------+
3 rows in set (0.00 sec)

Here is the query to add column −

mysql> alter table DemoTable add column Gender ENUM('MALE','FEMALE');
Query OK, 0 rows affected (0.55 sec)
Records :0 Duplicates : 0 Warnings : 0

Following is the query to insert data into a new column of an already existing table −

mysql> update DemoTable set Gender='FEMALE' where Id=2;
Query OK, 1 row affected (0.13 sec)
Rows matched − 1 Changed − 1 Warnings − 0

Let us check the table records once again −

mysql> select *from DemoTable;

This will produce the following output −

+----+------+--------+
| Id | Name | Gender |
+----+------+--------+
|  1 | John | NULL   |
|  2 | Bob  | FEMALE |
|  3 | Adam | NULL   |
+----+------+--------+
3 rows in set (0.00 sec)