Ordinal position notation, AKA ordinals, is column shorthand based on the column order in the list of columns in the SELECT cla
If I recall correctly, the use of ordinals like you describe is being deprecated by Microsoft in a future release of SQL Server. I could be wrong on this, but I think that's the case. I've always liked using them in certain cases because it involves less typing when you're dealing with derived columns that contain a longish query.