●문제 : 위와 같은 결과를 추출할 수 있는 한개의 SQL문을 작성하시오

내가 작성한 답안 :

select a.name, b.end, a.start
from test.quiz2 a, test.quiz2 b
where a.start <> b.end
and a.rowid - 1 = b.rowid
and a.name = b.name
group by b.rowid;

모범답안 :

select name, end_r start_date, start_l end_date
from (select name, sum(decode(no,1,start_dt)) start_l, sum(decode(no,1,end_dt)) end_l,
              sum(decode(no,2,start_dt)) start_r, sum(decode(no,2,end_dt)) end_r
     from (select name, start_dt, end_dt, rownum rn
           from (select name, start_dt, end_dt
                  from quiz2
                 order by name, start_dt, end_dt )) x, copy_t y
     where y.no <= 2
     group by name, decode(no,1,rn,rn+1)
  )
where end_r <> start_l;