join 문제풀이

6번문제 5-33p

select e.dep_id department, e.last_name employee, m.last_name colleague
from emp e join emp m
on (e.dep_id=m.dep_id)
and (e.last_name<>m.last_name)
order by e.dep_id, e.last_name, m.last_name

and(e.last_name<>m.last_name)이 중요
문제에 힌트가 너무 없고 결과를 보고 추리를 해야하기 때문에 찾아봤음.. 내 사고가 딸리나

7번문제 5-34p

select e.last_name, e.job_id, d.dep_name, e.sal, j.gra
from emp e join dep d
on (e.dep_id=d.dep_id)
join job_grades j
on e.sal between j.low_sal and j.high_sal