Are these two queries the same - GROUP BY vs. DISTINCT?

Question

These two queries seem to return the same results. Is that coincidental or are they really the same?

1.

SELECT t.ItemNumber,
  (SELECT TOP 1 ItemDes         


        

Answer 1

Yes they return the same results.

Normally the group by clause (found here) groups the rows by the specific column mentioned so if you have a sum in your select statement. Thus if you have a table like :

O_Id        OrderDate   OrderPrice      Customer
1           2008/11/12  1000            Hansen
2           2008/10/23  1600            Nilsen
3           2008/09/02  700             Hansen
4           2008/09/03  300             Hansen
5           2008/08/30  2000            Jensen
6           2008/10/04  100             Nilsen

If you group by customer and ask for the sum or the order price you will get

Customer    SUM(OrderPrice)
Hansen          2000
Nilsen             1700
Jensen          2000

Contrary to this the distinct (found here) just makes it so you don't have duplicate rows. In this case the original table would stay the same since each row is different from the others.