title: Is it possible to alter a SQL Server table column datatype from bigint to varchar after it has been populated?
body: <p>I have a SQL Server 2008 table which contains an external user reference currently stored as a bigint - the userid from the external table. I want to extend this to allow email address, open ID etc to be used as the external identifier. Is it possible to alter the column datatype from bigint to varchar without affecting any of the existing data?</p>