USE PUBS
SELECT CAST(title AS CHAR(65)) AS title
 , type
 , (SELECT AVG(price) 
      FROM
      (SELECT TOP 3 price
         FROM titles
        ORDER BY price DESC) 
      t) AS average_price
  FROM titles

title                                                             type         average_price         
----------------------------------------------------------------- ------------ --------------------- 
The Busy Executive's Database Guide                               business     21.8300
Cooking with Computers: Surreptitious Balance Sheets              business     21.8300
You Can Combat Computer Stress!                                   business     21.8300
Straight Talk About Computers                                     business     21.8300
Silicon Valley Gastronomic Treats                                 mod_cook     21.8300
The Gourmet Microwave                                             mod_cook     21.8300
The Psychology of Computer Cooking                                UNDECIDED    21.8300
But Is It User Friendly?                                          popular_comp 21.8300
Secrets of Silicon Valley                                         popular_comp 21.8300
Net Etiquette                                                     popular_comp 21.8300
Computer Phobic AND Non-Phobic Individuals: Behavior Variations   psychology   21.8300
Is Anger the Enemy?                                               psychology   21.8300
Life Without Fear                                                 psychology   21.8300
Prolonged Data Deprivation: Four Case Studies                     psychology   21.8300
Emotional Security: A New Algorithm                               psychology   21.8300
Onions, Leeks, and Garlic: Cooking Secrets of the Mediterranean   trad_cook    21.8300
Fifty Years in Buckingham Palace Kitchens                         trad_cook    21.8300
Sushi, Anyone?                                                    trad_cook    21.8300

(18 row(s) affected)

Das Beispiel macht zwar nicht übermässig viel Sinn, verdeutlicht aber gut den dahinterstehenden Grundgedanken.