Performance effect of using TOP 1 in a SELECT query

Question

I have a User table where there are a Username and Application columns. Username may repeat but combination of Username + Application is unique, but I don\'t have the unique con

Answer 1

I think it depends on the query execution plan that SQL generates ... In the past on previous versions of SQL Server I have seen the use of a superfluous 'TOP' deliver definite performance benefits with complex queries with many joins. But definitely not in all cases.

I guess the best advice I can give is to try it out on a case by case basis.