INSERT INTO a temp table, and have an IDENTITY field created, without first declaring the temp table?

Question

I need to select a bunch of data into a temp table to then do some secondary calculations; To help make it work more efficiently, I would like to have an IDENTITY column on that

Answer 1

To make things efficient, you need to do declare that one of the columns to be a primary key:

ALTER TABLE #mytable
ADD PRIMARY KEY(KeyColumn)

That won't take a variable for the column name.

Trust me, you are MUCH better off doing a: CREATE #myTable TABLE (or possibly a DECLARE TABLE @myTable) , which allows you to set IDENTITY and PRIMARY KEY directly.

Answer 2

IIRC, the INSERT INTO command uses the schema of the source table to create the temp table. That's part of the reason you can't just try to create a table with an additional column. Identity columns are internally tied to a SQL Server construct called a generator.