SQL Server: Insert missing Identity Column Values

When we set identity to a particular column, we dont need to pass value for that column.
SQL Server automatically increments its value.

Suppose if we inserts 10 records and deleted last record. Maximum value will be 9 but when we add new record then SQL server takes next value as 11 not it doesn't take 10. Because we already added record in 10th position and deleted after it.
Example:

CREATE TABLE [dbo].[Student](
[Sno] [int] IDENTITY(1,1) NOT NULL,
[Sname] [nvarchar](50) NULL,
[Saddrs] [nvarchar](50) NULL
) ON [PRIMARY]
GO

insert into student(sname,saddrs) values('Abhi','India')
insert into student(sname,saddrs) values('Sourav','Japan')
insert into student(sname,saddrs) values('david','US')
insert into student(sname,saddrs) values('rahul','UK')
insert into student(sname,saddrs) values('gautam','Australia')
insert into student(sname,saddrs) values('jonathan','Germany')
insert into student(sname,saddrs) values('prasad','Pune')
insert into student(sname,saddrs) values('sandeep','Pune')
insert into student(sname,saddrs) values('john','Pune')
insert into student(sname,saddrs) values('sanjay','Pune')

Now we will delete sno=10

delete from student where sno=10

After Record deleted

Now If we add new record then it will take sno=11 but we want to add sno=10
If you try to insert value at sno=10, it will give you an error as  shown in below screenshot.

In this case we need to insert value manually by turning off identity feature off. After inserted manually we need to identity turn on  again.

Syntax:
SET IDENTITY_INSERT TABLE-NAME  ON 

Example:
SET IDENTITY_INSERT student  ON

Here
SET IDENTITY_INSERT TABLE-NAME  ON :turns off identity increment. Specify table name on which you want to turn off identity

Your Insert Statement, you need to provide identity column value because in previous command you have turned off autoincrement. Provide missing identity values which you want to add.
Example: Student is table in which sno is identity column.
I have 10 records, i have deleted last record i.e sno=10 now i want to add value for sno=10

My query will be

insert into student(Sno,sname,saddrs) values(10,'sachin','Pune')

After Above Query Result will be

Syntax:
SET IDENTITY_INSERT TABLE-NAME  OFF
Example:
SET IDENTITY_INSERT student  OFF

Here
SET IDENTITY_INSERT TABLE-NAME  OFF:turns on identity increment.
Now your autoincrement will be started, you dont need to provide value for identity column.

Now If you try to provide value then sql server will give you an error.
Example:

insert into student(Sno,sname,saddrs) values(11,'Rakesh','Pune')

I hope this article helps you to understand how to insert missing identity column values.

Happy Coding!!