SQL Server, How to set auto increment after creating a table without data loss?

Question

I have a table table1 in SQL server 2008 and it has records in it.

I want the primary key table1_Sno column to be an auto-incrementing col

Answer 1

If you don't want to add a new column, and you can guarantee that your current int column is unique, you could select all of the data out into a temporary table, drop the table and recreate with the IDENTITY column specified. Then using SET IDENTITY INSERT ON you can insert all of your data in the temporary table into the new table.