2nd week for SQL
Group by name : make one group have same name.
Select name(범주 별로 세어주고 싶은 필드명), count(*) from users(테이블)
group by name(범주 별로 세어주고 싶은 필드명)
Select week, min(likes) from checkins
group by week -> week별 likes(최소값을 알고 싶은 필드명) 최소값
Select week, max(likes) from checkins
group by week -> 최대값
Select week, avg(likes) from checkins
group by week -> 평균값
Select week, sum(likes) from checkins
group by week -> 합계
Order by : sort by your need
Select * from users
order by name->오름차순
Select name, count(*) from users
group by name
order by count(*) desc;->내림차순
Order to operate query : from -> group by -> select(name, count(*))-> order by
Select payment_method, count(*) from orders
where course_title = ‘웹개발 종합반’
Group by payment_method
Order to operate query : from -> where -> group by -> select
We should know order to operate query to avoid error.
Example)
Select name, count(*) from users
where email like ‘%gmail.com’
group by name