Hugo Kornelis (12/17/2012)
(That being said - there is indeed no guarantee. SQL Server could come up with an execution plan that projects the SELECT list first, then reorders the rows. In that case, the second query would return no rows - sorting in an execution plan is a blocking operation, so the sort operator will not start returning rows until it has consumed the entire input, and in this hypothetic case the query would error out before the entire input has been consumed).
Good point. I was wrong to suggest that 1 row might be returned. Returning 1 row is not a possibility, only returning 0 rows or returning 2 rows, since the order by clause means that there is a sort either before the projection (so there will be two rows) or after the projection has been done for all rows (in which case there will be 0 rows).
Tom