How do you UPDATE an identity column in SQL azure? Is it possible?

问题

I have this code:

ALTER TABLE FishSticks
ADD MyNewIdentityColumnId INT IDENTITY(1,1) NOT NULL

SET IDENTITY_INSERT FishSticks ON

UPDATE FishSticks 
SET MyNewIdentityColumnId = MyOldColumnId

However it says:

Cannot update identity column 'MyNewIdentityColumnId'.

I assume this is due to SQL Azure, but I didn't have much success googling. It seems that changing a column to be an identity while preserving data is a huge difficulty.

回答1:

SET IDENTITY_INSERT only works for INSERTS and that error is not specific to SQL Azure. You'll get the same error on SQL Server/Express

to go around the issue, SET IDENTITY_INSERT to ON, reinsert all the column values from the existing row whose identity value you want to replace with a new value, SET IDENTITY_INSERT OFF, then delete the previous row.

回答2:

I found this Possible solution from Herve Roggero who basically gives a way of turning off the ID and then adding the rows, then turning ID back on.

来源：https://stackoverflow.com/questions/9214316/how-do-you-update-an-identity-column-in-sql-azure-is-it-possible