一段很费脑子的SQL

/*SQL> desc a
Name   Type         Nullable Default Comments
------ ------------ -------- ------- --------
ID     NUMBER(5)                             
COURSE VARCHAR2(40) Y                        
SCORE  NUMBER(3)    Y  */

----找每门课程的前两名

SELECT distinct a.*
  FROM a
where (SELECT count(b.id)
          FROM a b
         WHERE b.course = a.course
           and b.score > a.score) < 2
order by a.course,a.score desc

---end