In SQL Server, when you have a table with an identity column, you typically do not specify a value for that column when inserting new rows. The database automatically generates the value for the identity column. However, there are scenarios where you might want to explicitly insert a value into an identity column. This can be done by enabling the IDENTITY_INSERT setting for the table.

Here’s how you can do it:

1. Enable IDENTITY_INSERT: You need to set IDENTITY_INSERT to ON for the specific table where you want to insert explicit values into the identity column.

2. Insert with a Column List: When you perform the insert, you must specify a column list that includes the identity column.

3. Disable IDENTITY_INSERT: After the insert operation, it’s a good practice to set IDENTITY_INSERT back to OFF.

Example

Assuming you have a table named MyTable with an identity column named Id, here’s how you can insert an explicit value:

sql
1-- Step 1: Enable IDENTITY_INSERT
2SET IDENTITY_INSERT MyTable ON;
3
4-- Step 2: Insert with a column list
5INSERT INTO MyTable (Id, Column1, Column2)
6VALUES (1, 'Value1', 'Value2');
7
8-- Step 3: Disable IDENTITY_INSERT
9SET IDENTITY_INSERT MyTable OFF;

Important Notes:

• You can only have IDENTITY_INSERT set to ON for one table at a time in a session.
• If you try to insert a value into an identity column without enabling IDENTITY_INSERT, you will receive an error.
• Be cautious when inserting explicit values into an identity column, as it can lead to primary key violations if the value already exists or if it conflicts with the automatically generated values.

This method is useful for scenarios such as data migration, restoring data, or when you need to maintain specific identity values for business logic reasons.