sql - SQL の重複を排除するにはどうすればよいですか?

Question

学生 ID フィールドの重複をなくすために誰かが私を正しい方向に向けることができますか?

SQL> select DISTINCT(student_class.student_id) as student_Num,student_class.class_id,
  2  event.event_id, event.event_name
  3  from student_class, event
  4  where student_class.class_id = '10'
  5  and event.class_id = '10';

STUDENT_NUM   CLASS_ID   EVENT_ID EVENT_NAME
----------- ---------- ---------- --------------------------------------------------
         12         10          2 Flag FOOtball Game
         12         10          5 PICKUP SOCCER GAME
          9         10          5 PICKUP SOCCER GAME
         16         10          5 PICKUP SOCCER GAME
          6         10          2 Flag FOOtball Game
         18         10          5 PICKUP SOCCER GAME
          4         10          5 PICKUP SOCCER GAME
          4         10          2 Flag FOOtball Game
         16         10          2 Flag FOOtball Game
         20         10          2 Flag FOOtball Game
          3         10          5 PICKUP SOCCER GAME
          2         10          5 PICKUP SOCCER GAME
          3         10          2 Flag FOOtball Game
          8         10          2 Flag FOOtball Game
          9         10          2 Flag FOOtball Game
          2         10          2 Flag FOOtball Game
          6         10          5 PICKUP SOCCER GAME
         20         10          5 PICKUP SOCCER GAME
         18         10          2 Flag FOOtball Game
          8         10          5 PICKUP SOCCER GAME