Auto-increment is used to allow a unique number when a new record inserted into a table. Generally we use Auto-increment to create value for primary key field automatically when a new record is inserted into a table.

Syntax:

The below statement creates a table named "user" with the column "id" that will be auto-increment primary key field:

CREATE TABLE user
(
id int NOT NULL AUTO_INCREMENT,
first_name varchar(45),
last_name varchar(45),
PRIMARY KEY (id)
);

The AUTO_INCREMENT keyword is used to increment value in MySQL, by default it's starting value is 1 and increments by 1 every time when a new record is inserted.

We can start Auto-increment with another value apart from 1 by using the below statement:

ALTER TABLE user AUTO_INCREMENT=10;

Suppose you want to insert a new record into "user" table then you don't need to define value of id field, it will auto-increment "id" column automatically (a unique value will be assigned to id column) as below:

INSERT INTO Persons (first_name,last_name)
VALUES ('John','Simp');

Result

 user

id  first_name                  last_name
.......................................
1   John                        Simp              

Hope this will help you :)