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데이터 분석 기술 블로그

Japan Population _ Easy. HackerRank

SolutionSELECT SUM(POPULATION)FROM CITYWHERE COUNTRYCODE = 'JPN';
SQL/문제풀이 2024. 10. 31. 20:11
Employees Whose Manager Left the Company _ Easy. LeetCode

SolutionSELECT e.employee_idFROM Employees eLEFT JOIN Employees mON e.manager_id = m.employee_idWHERE (e.salary
SQL/문제풀이 2024. 10. 30. 20:11
Average Population _ Easy. HackerRank

SolutionSELECT ROUND(AVG(POPULATION))FROM CITY;
SQL/문제풀이 2024. 10. 29. 20:11
Triangle Judgement _ Easy. LeetCode

SolutionSELECT *, (CASE WHEN x + y   * 삼각형의 조건 : 제일 긴 변이 나머지 두 변의 합보다 작아야 한다.
SQL/문제풀이 2024. 10. 28. 20:11
Revising Aggregations - Averages _ Easy. HackerRank

SolutionSELECT AVG(POPULATION)FROM CITYWHERE DISTRICT = 'California';
SQL/문제풀이 2024. 10. 27. 20:11
Primary Department for Each Employee _ Easy. LeetCode *

SolutionSELECT employee_id, department_idFROM EmployeeWHERE primary_flag = 'Y' OR employee_id IN (SELECT employee_id FROM Employee GROUP BY employee_id HAVING COUNT(department_id) = 1); 1차 시도처음에는 예시만 보고 'primary_flag'가 'Y'이거나 employee_id = department_id인 데이터를 추출하려고 했으나 오답이었고 후자가 항상 맞지는 않다는 것을 알았다. 2차 시도SELECT employee_id, department_idFROM EmployeeWHERE primary_flag = 'Y'..
SQL/문제풀이 2024. 10. 26. 15:39
Revising Aggregations - The Sum Function _ Easy. HackerRank

SolutionSELECT SUM(POPULATION)FROM CITYWHERE DISTRICT = 'California';
SQL/문제풀이 2024. 10. 25. 20:10
The Number of Employees Which Report to Each Employee _ Easy. LeetCode *

SolutionSELECT e.employee_id, e.name, COUNT(r.employee_id) AS reports_count, ROUND(AVG(r.age), 0) AS average_ageFROM Employees eJOIN Employees rON e.employee_id = r.reports_toGROUP BY e.employee_id, e.nameORDER BY e.employee_id; 처음에는 다 구할 수 있었지만 reports_to에 대응하는 name을 찾을 수 없어서 검색해야만 했다. 확인해 보니 간단하게 JOIN으로 해결할 수 있었다...
SQL/문제풀이 2024. 10. 24. 11:24
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