[Tip]query

--조회 쿼리
select rownum, a.* 

from (select * from employees

      order by salary desc) a

where rownum between 1 and 10;

select * from (select rownum r, a.* 

               from (select * from employees

                     order by salary desc) a)

where r between &start and &end;

select * from (select rownum r, a.* 

               from (select * from employees

                     where last_name like '%&name%'

                     order by salary desc) a)

where r between &start and &end;



-- 열의 갯수가 일치해야 함.
select last_name from employees
union -- 합집합
select first_name from employees;

select last_name from employees
union all -- 중복포함
select first_name from employees;

select last_name from employees
minus -- 차집합
select first_name from employees;

select last_name from employees
intersect -- 교집합
select last_name from employees;