데이터 분석 기술 블로그

SolutionSELECT DISTINCT(CITY)FROM STATIONWHERE CITY REGEXP '[^aeiouAEIOU]$';

SolutionSELECT p.project_id, ROUND(AVG(e.experience_years), 2) AS average_yearsFROM Project pLEFT JOIN Employee eON p.employee_id = e.employee_idGROUP BY p.project_id;

SolutionSELECT DISTINCT(CITY)FROM STATIONWHERE CITY REGEXP '^[^aeiouAEIOU]';

SolutionSELECT p.product_id, ROUND(CASE WHEN SUM(u.units) IS NULL THEN 0 ELSE SUM(p.price * u.units) / SUM(u.units) END, 2) AS average_priceFROM Prices pLEFT JOIN UnitsSold uOn p.product_id = u.product_id AND u.purchase_date BETWEEN p.start_date AND p.end_dateGROUP BY p.product_id; Solution 2SELECT p.product_id, ROUND(COALESCE(SUM(p.price * u.units) / SUM(u.uni..

SolutionSELECT DISTINCT(CITY)FROM STATIONWHERE CITY REGEXP '^[^aeiouAEIOU]'; 모음이 시작하지 않도록 하려면 [] 이 bracket 안에다가 not을 의미하는 ^를 넣어주면 된다.

SolutionSELECT *FROM CinemaWHERE id % 2 = 1 AND description != 'boring'ORDER BY rating DESC;

SolutionSELECT CITYFROM STATIONWHERE CITY REGEXP '[aeiouAEIOU]$' AND CITY REGEXP '^[aeiouAEIOU]';

SolutionSELECT st.student_id, st.student_name, su.subject_name, COUNT(ex.student_id) AS attended_examsFROM Students stCROSS JOIN Subjects suLEFT JOIN Examinations exON st.student_id = ex.student_id AND su.subject_name = ex.subject_nameGROUP BY st.student_id, st.student_name, su.subject_nameORDER BY st.student_id ASC, su.subject_name ASC;1. CROSS JOIN과 LEFT JOIN은 동시에 쓸 수 있다는 것을 몰랐다.2...