Jerry의 컴퓨터 일기 💻

https://leetcode.com/problems/trips-and-users/description/🗒️SQL 코드 풀이 1SELECT T1.request_at AS Day, ROUND( SUM(CASE WHEN status = "completed" THEN 0 ELSE 1 END) / COUNT(*),2) AS "Cancellation Rate" FROM Trips T1 LEFT JOIN Users U1 ON T1.client_id= U1.users_id LEFT JOIN Users U2 ON T1.driver_id= U2.users_id WHERE U1.banned "YES" AND U2.banned "YES" ..

https://leetcode.com/problems/department-top-three-salaries/description/🗒️SQL 코드 풀이 1SELECT D1.name AS Department , E1.name AS Employee , E1.salary AS Salary FROM ( SELECT *, DENSE_RANK() OVER (PARTITION BY departmentId ORDER BY salary DESC) AS salaryRank FROM Employee ) E1 INNER JOIN Department D1 ON E1.departmentId = D1.id WHERE E1.salaryRank  ..

https://leetcode.com/problems/consecutive-numbers/description/?envType=study-plan-v2&envId=top-sql-50🏫  추가 학습 (Window Function) 참고로 OVER()는 윈도우 함수가 적용될 데이터 범위를 정하는 역할이다. 순위 함수 (Ranking Functions)SELECT id, num, ROW_NUMBER() OVER(ORDER BY num) AS row_num, RANK() OVER(ORDER BY num) AS rank_num, DENSE_RANK() OVER(ORDER BY num) AS dense_rank_numFROM Logs;ROW_NUMBER()정렬 순서대로 고유한 순위..

https://leetcode.com/problems/primary-department-for-each-employee/?envType=study-plan-v2&envId=top-sql-50🗒️SQL 코드 풀이 SELECT employee_id , department_id FROM EmployeeWHERE employee_id IN ( SELECT employee_id FROM Employee GROUP BY employee_id HAVING COUNT(*) = 1 )OR primary_flag = "Y" 1. 조건이 2개가 있다. primary_flag 1개 밖에 없는 경우primary_flag가  Y인 경우 2.  이 두가지를 WHERE로..

https://leetcode.com/problems/biggest-single-number/description/?envType=study-plan-v2&envId=top-sql-50🗒️SQL 코드 풀이 SELECT MAX(A.num) AS num FROM ( SELECT * FROM MyNumbers GROUP BY num HAVING COUNT(num) = 1 ) A 1. 간단하게 풀이 가능한 문제이다. 2. GROUP BY 와 HAVING으로 중복되는 숫자를 제거한 서브쿼리를 만든다. 3. 해당 서브쿼리를 가져와 MAX 값을 추출한다.  문제 한번 더 돌아보기SELECT * FROM ..

https://leetcode.com/problems/product-sales-analysis-iii/?envType=study-plan-v2&envId=top-sql-50🗒️SQL 코드 풀이 SELECT A.product_id , A.year AS first_year ,quantity ,price FROM Sales A INNER JOIN ( SELECT product_id , MIN(year) AS year FROM Sales GROUP BY product_id )B ON A.product_id = B.product_id AND A.year = B.year 1. produ..

https://leetcode.com/problems/game-play-analysis-iv/?envType=study-plan-v2&envId=top-sql-50🗒️SQL 코드 풀이 SELECT ROUND(COUNT(DISTINCT S.player_id) / COUNT(DISTINCT A.player_id ),2) AS fraction FROM Activity A LEFT JOIN ( SELECT player_id, (MIN(event_date) + INTERVAL 1 DAY) AS seq_day FROM Activity GROUP BY player_id ) S ON A.event..

https://leetcode.com/problems/immediate-food-delivery-ii/submissions/1562280627/?envType=study-plan-v2&envId=top-sql-50🗒️SQL 코드 풀이 # Write your MySQL query statement belowSELECT ROUND( SUM( CASE WHEN kind_of_delivery = "immediate" THEN 1 ELSE 0 END ) * 100 / COUNT(*), 2 ) AS immediate_percentage FROM ( SELEC..

https://leetcode.com/problems/percentage-of-users-attended-a-contest/?envType=study-plan-v2&envId=top-sql-50🗒️SQL 코드 풀이 SELECT R.contest_id, ROUND(COUNT(DISTINCT R.user_id)/(SELECT COUNT(DISTINCT user_id)FROM Users)*100 ,2) percentage FROM Register R GROUP BY contest_id ORDER BY percentage DESC, contest_id 1. 메인 테이블은 Register의 테이블이다.  2. Register 테이블을 cont..

https://leetcode.com/problems/average-selling-price/description/?envType=study-plan-v2&envId=top-sql-50🗒️SQL 코드 풀이 SELECT P.product_id, CASE WHEN SUM(U.units)0 THEN ROUND(SUM(P.price * U.units)/SUM(U.units),2) ELSE 0 END AS average_price FROM Prices P LEFT JOIN UnitsSold U ON P.product_id = U.product_id AND U.purchase_date = P.start_date GROUP BY P.pr..