[데이터분석] 코드카타 94

https://leetcode.com/problems/percentage-of-users-attended-a-contest/description/

 

94. Percentage of Users Attended a Contest

Write a solution to find the percentage of the users registered in each contest rounded to two decimals.

Return the result table ordered by percentage in descending order. In case of a tie, order it by contest_id in ascending order.

The result format is in the following example.

 

(오답)  % 구하려면 각 sum 한 걸 나눠야하나..?

select r.contest_id,

          round(count(u.user_id)/count(r.user_id),2) percentage

from Users u join Register r on u.user_id = r.user_id

group by 1

order by 2 desc, 1

 

 

(오답) % 를 구하기 위해 *100 추가.

select r.contest_id,

           round(count(u.user_id)/count(r.user_id)*100,2) percentage

from Users u join Register r on u.user_id = r.user_id

group by 1

order by 2 desc, 1

 

 

(정답) 왜 Users 테이블에서 전체 count 를 한 값으로 나누는 것인지 모르겠다..!

select r.contest_id,

          round(count(u.user_id)/(select count(*) from Users)*100,2) percentage

from Users u join Register r on u.user_id = r.user_id

group by 1

order by 2 desc, 1