How to update Identity Column in SQL Server?
To modify an identity column, use the following commands:
Make sure that the new values do not conflict with any constraints, and remember that IDENTITY_INSERT can only be enabled for one table at a time.
The nature of the Identity Column
The SQL Server identity column is auto-incrementing and read-only. It is the go-to for unique primary keys. Situations may arise requiring you to override this behavior - proceed with care.
Identity reseeding in action
To reset the identity value to a new seed:
This changes the starting value for new entries and not for existing data.
Using the IDENTITY_INSERT setting
While the SET IDENTITY_INSERT command allows you to change identity values, frequent use may lead to integrity issues and potential headaches. Always create a backup before and test it out in a dev environment first.
Safe identity column update: the delete and reinsert approach
When updating an identity column, another viable approach is to delete the record and then reinsert it:
- Backup your table (because better safe than sorry).
- Flip the IDENTITY_INSERT switch to ON.
- Insert the record with the desired value.
- Remove the old record.
- Turn IDENTITY_INSERT back to OFF.
Keeping this order prevents relational integrity issues and unwanted trigger activations.
Handling wider scale identity changes
For large identity changes:
- Transfer data to a temporary table first.
- Remove constraints, but remember that with great power comes great responsibility!
- Update those identity values.
- Move back the data.
- Reapply constraints and hope you haven't broken anything.
Keep stakeholders in the loop about what you're doing and why.
Design methods for dealing with persistent identity issues
If you're frequently battling with identity values, consider a table redesign, leveraging management views for efficient reconstruction.
What about gaps in identity values?
Post deletions or resets, you'll likely encounter gaps in your identity sequence. You could comb through them or just learn to live with the void. Or, consider a reseed:
But remember, every action has a reaction. Be aware of potential limitations and changes in performance.
Clash of the identities: resolving insertion conflicts
During reseeding, ensure unique values to prevent conflicts. If you hit a duplicate, it's error time. Maintain this uniqueness across related tables.
Ensuring data integrity when updating an identity column
Remember to keep referential integrity intact when using SET_IDENTITY_INSERT. Relationships can be complex - nobody wants orphan records or constraint violations!
Addressing identity value gaps
After deleting records or resetting the identity column, gaps in your identity sequence are likely. You can either opt to live with them or reseed if needed.
Designing for resilience: considering the broader impact
Understanding the full scope of potential impacts to your database schema is crucial. Disruptions to operations and data relationships can occur, and it's important to manage these changes in the interest of long-term stability.
Was this article helpful?