[데이터베이스]

hr

select department_id, first_name from employees;
select department_id, department_name from departments;

select count(*) from employees;         -- 107
select count(*) from departments;       -- 27

select
    E.department_id, D.department_name, E.first_name
        from employees E, departments D;
        
select
    E.department_id, E.first_name, D.department_name, E.salary
        from employees E
        join departments D
            on D.department_id = E.department_id;
            
---------------------------------------------------------------
select
    E.employee_id as 사원번호,
    E.first_name || ' ' || E.last_name as 이름,
    E.salary as 급여,
    D.department_id as 부서번호,
    D.department_name as 부서명
        from employees E
        join departments D
            on e.department_id = d.department_id
        where
            E.salary >= 10000
        order by
            E.department_id, E.salary desc;

Student

show user;

create table student (
    idx     number,
    name    varchar2(100)

);
create table report_card (
    idx     number,
    score   number
);
insert into student values (1, '짱구');
insert into student values (2, '유리');
insert into student values (3, '철수');

insert into report_card values (1, 72);
insert into report_card values (2, 67);
insert into report_card values (3, 93);

commit;

select S.idx, S.name, R.score from student S
    join report_card R
        on S.idx = R.idx;