How Can I Modify Identity Column Values in SQL Server?

Updating Identity Columns in SQL Server

For those seeking to modify the identity column in SQL Server, it's crucial to understand that direct updates are not permitted. Unlike regular columns, identity columns cannot be simply updated using an update statement.

Alternatives to Identity Column Updates

While updating an identity column directly is impossible, there are alternative approaches to achieve similar results:

Updating Identity Values for New Records

To ensure that new records start with a specific identity value, use DBCC CHECKIDENT. This command checks the current identity value and resets it if necessary.

DBCC CHECKIDENT('tableName', RESEED, NEW_RESEED_VALUE)

Updating Identity Values for Existing Records

To selectively update the identity values of existing records, utilize IDENTITY_INSERT. This feature allows explicit insertion of values into the identity column.

SET IDENTITY_INSERT YourTable {ON|OFF}

Example

To insert a new record with a specific identity value:

-- Enable identity insert
SET IDENTITY_INSERT YourTable ON

-- Insert record
INSERT INTO YourTable(IdentityCol, otherCol) VALUES(13,'myValue')

-- Disable identity insert
SET IDENTITY_INSERT YourTable OFF

To update an existing record:

-- Delete old record
DELETE FROM YourTable WHERE ID=3

-- Insert record with new identity value
SET IDENTITY_INSERT YourTable ON
INSERT INTO YourTable(ID, otherCol) VALUES(13,'newValue')
SET IDENTITY_INSERT YourTable OFF

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