[sql] Why is SQL server throwing this error: Cannot insert the value NULL into column 'id'?

I had a similar problem and upon looking into it, it was simply a field in the actual table missing id (id was empty/null) - meaning when you try to make the id field the primary key it will result in error because the table contains a row with null value for the primary key.

This could be the fix if you see a temp table associated with the error. I was using SQL Server Management Studio.