SQL
1.SQL 중급 - Group By & Having
COUNT AVG 종합 사용 Group By + Order By 
We define an employee's total earnings to be their monthly worked, and the maximum total earnings to be the maximum total earnings for any employee i
3.SQL ) Case-When-End
https://extbrain.tistory.com/46
4.184. Department Highest Salary_서브쿼리
https://leetcode.com/problems/department-highest-salary/
5.Challenges
https://www.hackerrank.com/challenges/challenges/problem?isFullScreen=true
6.Top Earners
https://www.hackerrank.com/challenges/earnings-of-employees/problem?h_r=internal-search
7.SQL 중급 ) UNION, UNION ALL
: 데이터를 위아래로 연결 두 개 테이블의 컬럼 수, 컬럼 데이터 형식이 모두 일치해야한다.UNION 연산은 두 개의 테이블을 하나로 합치면서 중복된 데이터를 제거한다.UNION은 정렬을 발생시킨다.Two pairs (X1, Y1) and (X2, Y2) are sai
8.SQL 중급 ) CASE를 활용한 테이블 피봇
백문이불여일타CASE를 활용한 테이블 피봇https://www.w3schools.com/sql/trysql.asp?filename=trysql_select_all
9.SQL 중급 ) 해커랭크_Type of Triangle
Write a query identifying the type of each record in the TRIANGLES table using its three side lengths. Output one of the following statements for each
10.180. Consecutive Numbers_조인,윈도우함수
https://leetcode.com/problems/consecutive-numbers/
11.The Report_조인
https://www.hackerrank.com/challenges/the-report/problem?h_r=internal-search
12.SQL) 윈도우 함수 뿌시기
13.184. Department Highest Salary_윈도우함수(MAX)
https://leetcode.com/problems/department-highest-salary/
14.SQL 중급 ) JOIN
문제:Given the CITY and COUNTRY tables, query the names of all cities where the CONTINENT is 'Africa'.Note: CITY.CountryCode and COUNTRY.Code are matchi
15.185. Department Top Three Salaries_윈도우함수(DENSE_RANK())
https://leetcode.com/problems/department-top-three-salaries/
16.184. Department Highest Salary_윈도우함수(RANK())
https://leetcode.com/problems/department-highest-salary/description/
17.[백문이불여일타:고급] 정규표현식 응용
https://www.hackerrank.com/challenges/weather-observation-station-6/problem?isFullScreen=true
18.사용자 정의 함수 (User-Defined Function)
with 데이터리안:데이터분석 고급
19.❌ 177. Nth Highest Salary (Case,If, Limit,Offset)
Case,If, Limit,Offset 를 활용해서 3가지 방법으로 풀기
20.[MySQL]CASE vs IF Statement vs IF function
CASE vs IF Statement vs IF function 비교
21.WITH AS
임시테이블을 만드는 효과반복 쿼리문을 줄여서 테이블 엑세스를 줄이고 쿼리문 단순화 다중 with as 구문 with절을 사용한 절이 성능이 더 높다