How to update Identity Column in SQL Server?

update table
set identity_column_name = some value

It is not an easy process and it is not advisable to use it, as there may be some foreign key associated on it.

 You can't update the Identity column as you update the normal ones

But here are steps to do it, Please take a back-up of table

Step 1- Select design view of the table

Step 2- Turn off the identity column

Now you can use the update query.

Now redo the step 1 and step 2 and Turn on the identity column

(OR)

USE DBCC CHECKIDENT

DBCC CHECKIDENT('tableName', RESEED, NEW_RESEED_VALUE)

If you want to update the value of identity column of existing records then you need to set

set identity_insert YourTable ON

Example

-- Set Identity insert on so that value can be inserted into this column
SET IDENTITY_INSERT YourTable ON
GO
-- Insert the record which you want to update with new value in identity column
INSERT INTO YourTable(IdentityCol, otherCol) VALUES(13,'myValue')
GO
--Now set the idenetity_insert OFF to back to prevoius track
SET IDENTITY_INSERT YourTable OFF