5 Tips for Resetting an Identity Column in SQL

To reset the identity column in a SQL table, you can use the following steps:

  1. First, make a backup of your table. This is important because resetting the identity column will cause data loss.
  2. Then, you can use the SET IDENTITY_INSERT statement to allow explicit values to be inserted into the identity column.
  3. Next, you can use the UPDATE statement to set the value of the identity column to the desired value for each row in the table.
  4. After all the rows have been updated, you can use the SET IDENTITY_INSERT statement again to disable the ability to insert explicit values into the identity column.
  5. Finally, you can use the DBCC CHECKIDENT command to reset the seed and increment values for the identity column.

Here is an example of how you can reset the identity column in a table called MyTable:

-- Make a backup of the table
SELECT * INTO MyTable_Backup FROM MyTable;

-- Enable the ability to insert explicit values into the identity column
SET IDENTITY_INSERT MyTable ON;

-- Update the values in the identity column
UPDATE MyTable
SET ID = NEW_ID
FROM (
  SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS NEW_ID, *
  FROM MyTable
) AS T

-- Disable the ability to insert explicit values into the identity column
SET IDENTITY_INSERT MyTable OFF;

-- Reset the seed and increment values for the identity column
DBCC CHECKIDENT('MyTable', RESEED, 0);

Note that this will reset the identity column to start at 1 and increment by 1 for each new row that is inserted into the table. You can customize the seed and increment values by specifying them in the DBCC CHECKIDENT command.