Resetting Identity Column Value

Identity column of a table is a column whose value increases automatically. A user generally cannot insert a value into an identity column. A table can have only one column that is defined with the identity attribute.

Syntax :

IDENTITY [ ( seed , increment ) ]

Default value of identity is IDENTITY (1,1).

Seed : The seed represents the starting value of an ID and the default value of seed is 1.

Increment : It will represent the incremental value of the ID and the default value of increment is 1.

For Example :

Step 1 : Create a table named school.

CREATE TABLE school (
student_id INT IDENTITY,
student_name VARCHAR(200),
marks INT
);

Here, the ‘student_id’ column of the table starts from 1 as the default value of seed is 1 and each row is incremented by 1.

Step 2 : Insert some value into a table.

INSERT INTO school (student_name, marks) VALUES ('Sahil', 100);
INSERT INTO school (student_name, marks) VALUES ('Raj', 78);
INSERT INTO school (student_name, marks) VALUES ('Navneet', 80);
INSERT INTO school (student_name, marks) VALUES ('Rahul', 75);
INSERT INTO school (student_name, marks) VALUES ('Sudeep', 82);
INSERT INTO school (student_name, marks) VALUES ('Azaan', 75);

Step 3 : To see the records in the table ‘school’ , we can use the following code:

SELECT * FROM school;

Output :

Step 4 : Lets delete a record.

DELETE FROM school WHERE student_id = 4;

Step 5 : To see the records in the table.

SELECT * FROM school;

Output :

Now, you can see that the student_id column is not in order, So you have to reset the Identity Column. 

Reset the Identity Value Using the DBCC CHECKIDENT Method :

Here, to reset the Identity column  in SQL Server you can use DBCC CHECKIDENT method.

Syntax :

DBCC CHECKIDENT ('table_name', RESEED, new_value);