where은 select 퀴리문으로 가져올 데이터 조건을 걸어주는걸 의미한다!
'같지않음' 조건(!=)
select * from orders
where course_title != "웹개발 종합반"
'범위' 조건(between)
select * from orders
where created_at between "2020-07-13" and "2020-07-15"
'포함' 조건(,)
select * from checkins
where week in (1, 3)
'문자열' 규칙 조건(like)
select * from users
where email like '%daum.net';