Here is the question I received on SQLAuthority Fan Page.

“How do I add an identity column to Table in SQL Server? “

Sometime the questions are very very simple but the answer is not easy to find.

Scenario 1:

If you are table does not have identity column, you can simply add the identity column by executing following script:

ALTER TABLE MyTable
  ADD ID INT IDENTITY(1,1) NOT NULL

Scenario 2:

If your table already has a column which you want to convert to identity column, you can’t do that directly. There is a workaround for the same which I have discussed in depth over the article Add or Remove Identity Property on Column.

Scenario 3:

If your table has already identity column and you can want to add another identity column for any reason – that is not possible. A table can have only one identity column. If you try to have multiple identity column your table, it will give following error.

Msg 2744, Level 16, State 2, Line 2
Multiple identity columns specified for table ‘MyTable‘. Only one identity column per table is allowed.

Leave a comment if you have any suggestion.

Reference : Pinal Dave (http://blog.SQLAuthority.com)