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윈도우 함수에서만 가능한 데이터 순위 정하기 1. MySQL ROW_NUMBER Function https://www.mysqltutorial.org/mysql-window-functions/mysql-row_number-function/ MySQL ROW_NUMBER and Its Useful Applications In this tutorial, you will learn about the MySQL ROW_NUMBER() function and how to use it to generate a unique number for each row in the result set. www.mysqltutorial.org SELECT ROW_NUMBER() OVER ( ORDER BY productName ..

1. MySQL LEAD Function LEAD()함수는 현재 행에서 여러 행을 보고 해당 행의 데이터에 액세스 할 수 있는 윈도우 함수입니다. LAG()함수와 비슷하며, LEAD()기능은 현재 행과 동일한 결과 집합 내의 후속 행과의 차이를 계산하기위해 매우 유용하다. LEAD([,offset[, default_value]]) OVER ( PARTITION BY (expr) ORDER BY (expr) ) 이 LEAD()함수는 정렬된 파티션 expression의 offset-th행에서의 값을 반환합니다 . 예시) orders and customers tables SELECT customerName, orderDate, LEAD(orderDate,1) OVER ( PARTITION BY customer..

181. Employees Earning More Than Their Managers https://leetcode.com/problems/employees-earning-more-than-their-managers/ Employees Earning More Than Their Managers - 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 The Employee table holds all employees including their managers. Ev..

더보기 한 줄 요약 - INNER JOIN은 INNER JOIN할 원래 테이블에 찾는 테이블 값이 있으면, 찾는 테이블 값만 출력 - OUTER JOIN은 OUTER JOIN할 원래 테이블에 찾는 테이블 값이 있으면, 원래 테이블+찾는 테이블 값 출력 1. 정의 INNER JOIN - 서로 매칭되는 것만 엮어 조회한다. ​OUTER JOIN - 매칭 뿐만 아니라 매칭되지 않은 데이터도 함께 조회한다. OUTER JOIN에는 Left Outer Join, Right Outer Join, Full Outer Join이 있다. Left Join, Right Join은 미매칭 데이터도 조회할 테이블 방향이다. 따라서 Left Outer Join의 경우 왼쪽에 기입한 테이블이 매칭여부와 상관없이 모두 조회된다. ..

The Report Problem The Report | HackerRank Write a query to generate a report containing three columns: Name, Grade and Mark. www.hackerrank.com You are given two tables: Students and Grades. Students contains three columns ID, Name and Marks. Ketty gives Eve a task to generate a report containing three columns: Name, Grade and Mark. Ketty doesn't want the NAMES of those students who received a ..

Top Earners Problem Top Earners | HackerRank Find the maximum amount of money earned by any employee, as well as the number of top earners (people who have earned this amount). www.hackerrank.com We define an employee's total earnings to be their monthly salaryXmonths worked, and the maximum total earnings to be the maximum total earnings for any employee in the Employee table. Write a query to ..

Weather Observation Station 9 Problem Weather Observation Station 9 | HackerRank Query an alphabetically ordered list of CITY names not starting with vowels. www.hackerrank.com Query the list of CITY names from STATION that do not start with vowels. Your result cannot contain duplicates. Solution SELECT DISTINCT CITY FROM STATION WHERE SUBSTR(CITY, 1, 1) NOT IN ('a','e','i','o','u'); SELECT DIST..

Japanese Cities' Attributes Problem Query all attributes of every Japanese city in the CITY table. The COUNTRYCODE for Japan is JPN. The CITY table is described as follows: Japanese Cities' Attributes | HackerRank Query the attributes of all the cities in Japan. www.hackerrank.com Solution SELECT * FROM CITY WHERE countrycode = 'JPN'