Worth noting that you can use use " select * " rather than " select 1 " or " select 12345 " for that matter.

I have a sneaking suspicion that using select * or select column could result in a bookmark lookup (or RID lookup) if your query includes columns that are non-clustered index columns or non-indexed columns (particularly in the WHERE clause or in joins).  Select 1 or select 12345 shouldn't encounter that problem.