1-1 데이터베이스에서 내가 원하는 데이터 잘 꺼내오기 (read)
- select, where, group by, order by, join, subquery, 그외
1-3 테이블 / 필드
- 실행 : Ctrl+Enter
- show tables : [테이블명] 확인
- select * from orders[테이블명] : 필드명, 값 확인 (너무 많으면 limit)
select order_no, created_at, user_id, email from orders
1-4 where 절
select * from orders where payment_method = 'kakaopay'
select * from point_users where point >= 5000
select * from orders where course_title = '앱개발 종합반' and payment_method = 'CARD'
select * from point_users where point > 20000
select * from users where name = '황**'
select * from orders where course_title = '웹개발 종합반' and payment_method = 'CARD'
- 대소문자 구분 없음 : 'card'도 결과 동일, but 맞춰주는 게 좋음
- ''가 없으면 테이블 또는 필드명으로 인식, 문자와 시간은 ''하고 숫자는 ''안한다
- 띄어쓰기 구분 있음
- 같지 않음 : !=
select * from orders where course_title != '웹개발 종합반' - 범위 : between A and B
select * from orders where created_at between '2020-07-13' and '2020-07-15' - 포함 : 필드명 in ( , , ...)
select * from checkins where week in(1,3) - 패턴 : 필드명 like '%'
select * from users where email like '%daum.net'
select * from orders where payment_method != 'CARD'
select * from point_users where point between 20000 and 30000
select * from users where email like 's%com'
select * from users where email like 's%com' and name = '이**'
- 마지막줄에 limit 숫자
- distinct : 중복 제거하고 보기
select distinct(payment_method) from orders - count : 세기
select count(distinct(name)) from users
1-6 퀴즈 풀기
select email from users where name = '남**'
select count(*) from users where email like '%gmail.com' and created_at between '2020-07-12' and '2020-07-14'
