해리문의 데이터_log

HackerRank Intermediate - SQL Project Planning이전 포스팅에서 다뤘던 해커랭크 SQL Project Planning 문제 풀이가 너무 복잡해서 간단한 버전의 풀이 방법을 고민하다가 답을 찾아서 다시 포스팅 해본다..ㅋㅋ 👉[TIL] 다중 CTE 활용한 복잡한 문제 해결 # MySQL # SQL👉 문제 바로가기(HackerRank) [간단 버전 풀이]SELECT t1.Start_Date, MIN(t2.End_Date)FROM (SELECT Start_Date FROM Projects WHERE Start_Date NOT IN (SELECT End_Date FROM Projects)) t1, (SELECT End_Date ..

HackerRank Intermediate - SQL Project Planning👉 문제 바로가기(HackerRank)WITH CTE AS ( SELECT Task_ID, Start_Date, End_Date FROM Projects WHERE End_Date NOT IN (SELECT Start_Date FROM Projects) ORDER BY Start_Date ), CTE_2 AS ( SELECT t1.Task_ID, t1.Start_Date, t1.End_Date, t2.Start_Date AS Start_Date_2, t2.End_Date AS End_Date_2 FROM Projects t1 LEFT OUTER JOIN CT..

HackerRank Intermediate - Weather Observation Station 20👉 문제 바로가기(HackerRank)-- Query the median of the Northern Latitudes (LAT_N) from STATION-- Round result to 4 decimal placesSELECT ROUND(t.LAT_N, 4)FROM (SELECT LAT_N, ROW_NUMBER() OVER(ORDER BY LAT_N) as rnk FROM STATION) tWHERE t.rnk = ((SELECT ROW_NUMBER() OVER(ORDER BY LAT_N DESC) as rnk FROM STATION ORDER..

HackerRank Intermediate - Binary Tree Nodes👉 문제 바로가기(HackerRank)-- Find the node type of Binary Tree(Root, Leaf, Inner)-- Order by the value of the node-- 풀이1) IN 구문 활용SELECT N, CASE WHEN P IS NULL THEN 'Root' WHEN P IS NOT NULL AND N NOT IN (SELECT P AS N FROM BST WHERE P IS NOT NULL) THEN 'Leaf' ELSE 'Inner' END AS NODEFROM BSTORDER BY N-- 풀이2) EXISTS 구문..