웅겹살의 프로그래밍 삼매경

row 를 array 또는 string으로 변환하기 1. unnest() 는 array 데이터를 row로 변환 unnest 결과는 하단의 내용과 같다 2. array_agg, array_agg_string 적용 결과는 하단의 내용과 같다 array_agg 는 group by와 함께 사용하는 함수이다. group by 된 값들을 array로 반환. distinct 와 order by 를 함께 이용하면 중복제거된 값을 구하거나, 원하는 순서로 정렬하여 array를 만들 수 있다. ex : array_agg(distinct col2 order by col2) -- 임시테이블 생성하여 테스트진행 with make_array as ( select unnest(array['고기', '고기', '고기', '채소', ..

https://programmers.co.kr/learn/courses/30/lessons/59044 코딩테스트 연습 - 오랜 기간 보호한 동물(1) ANIMAL_INS 테이블은 동물 보호소에 들어온 동물의 정보를 담은 테이블입니다. ANIMAL_INS 테이블 구조는 다음과 같으며, ANIMAL_ID, ANIMAL_TYPE, DATETIME, INTAKE_CONDITION, NAME, SEX_UPON_INTAKE는 각각 동물의 아이디 programmers.co.kr mySql SELECT I.NAME, I.DATETIME FROM ANIMAL_INS AS I LEFT JOIN ANIMAL_OUTS AS O ON I.ANIMAL_ID = O.ANIMAL_ID WHERE I.ANIMAL_ID NOT IN (..

https://leetcode.com/problems/rank-scores/ Rank Scores - LeetCode Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com -- MYSQL SELECT score , DENSE_RANK() OVER (ORDER BY score DESC ) 'rank' FROM Scores; -- ORACLE SELECT score , DENSE_RANK() OVER (ORDER BY score DESC ) as rank FROM Scores;

https://leetcode.com/problems/department-highest-salary/ Department Highest Salary - LeetCode Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com 부서별 salary가 가장높은 친구들 뽑기

https://leetcode.com/problems/nth-highest-salary/ Nth Highest Salary - LeetCode Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com 함수(Function) 문제가 나타났다 Mysql Oracle

https://leetcode.com/problems/second-highest-salary/ Second Highest Salary - LeetCode Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com salary가 2번째로 높은친구 뽑기 예외조건은 row가 1개일경우 null 출력 MYSQL Oracle

https://leetcode.com/problems/rising-temperature/ Rising Temperature - LeetCode Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com 어제보다 온도가 높은 id출력 Oracle Mysql

https://leetcode.com/problems/reformat-department-table/ Reformat Department Table - LeetCode Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com 각 부서의 월별 수익현황 출력 1-3월만 존재 4-12월 내역은 null 더 좋은방법이 있는지는 추후에 찾아보는걸로..

https://leetcode.com/problems/customers-who-never-order/ Customers Who Never Order - LeetCode Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com 주문안한 고객 찾아내기 not exists를 이용하며 풀이했다 심플!

https://leetcode.com/problems/duplicate-emails/ Duplicate Emails - LeetCode Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com LeetCode SQL문제풀이 시작 문제는 심플하다 중복된 이메일이 1개 초과인 이메일을 뽑아내면된다. select email from Person group by email having count(email) > 1 심플!!