How Can I Manage Identity Column Values in SQL Server?

Managing Identity Columns in SQL Server

Identity columns provide unique, sequential identifiers for rows in a database table. By default, SQL Server assigns an incrementing value to this column upon row insertion. However, there are instances where you may encounter a situation where the initial value is undesirably large or conflicts with an existing table relationship.

Can Identity Columns Be Updated?

Unlike regular columns, identity columns cannot be directly updated using an UPDATE statement. SQL Server restricts such modifications to preserve their sequential integrity and avoid data integrity issues.

Alternatives to Update Identity Columns

While updating identity columns directly is not possible, there are alternative approaches depending on your specific scenario:

1. Adjusting Identity Values for New Records:

To change the identity value for new records, use the following steps:

• Execute DBCC CHECKIDENT('tableName', RESEED, NEW_RESEED_VALUE). Replace 'tableName' with your actual table name and 'NEW_RESEED_VALUE' with the desired starting value. This command checks the current identity value and adjusts it to the specified value if necessary.

2. Updating Identity Values for Existing Records:

To update the identity value for existing records, you can use the IDENTITY_INSERT command as follows:

• Set IDENTITY_INSERT YourTable ON
• Insert the record with the desired identity value and other columns as needed.
• Delete the original record.
• Set IDENTITY_INSERT YourTable OFF

SET IDENTITY_INSERT YourTable ON
INSERT INTO YourTable(IdentityCol, otherCol) VALUES(13,'myValue')
DELETE FROM YourTable WHERE ID=3
SET IDENTITY_INSERT YourTable OFF

Remember to proceed cautiously with this approach, as modifying existing records may affect relationships and referential integrity constraints. It is recommended to create backups before performing such updates.

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