题目链接:点击打开链接
题目大意:略。
解题思路:注意解决方案(1) LEFT 玩法。
AC 代码
-- 解决方案(1) SELECT COUNTRY_NAME, CASE WHEN AVG(WEATHER_STATE) <= 15 THEN 'Cold' WHEN AVG(WEATHER_STATE) >= 25 THEN 'Hot' ELSE 'Warm' END AS WEATHER_TYPE FROM COUNTRIES AS C INNER JOIN WEATHER AS W ON C.COUNTRY_ID = W.COUNTRY_ID WHERE LEFT(DAY, 7) = '2019-11' GROUP BY 1; -- 解决方案(2) SELECT country_name, IF(AVG(weather_state) <= 15, 'Cold', IF(AVG(weather_state) >= 25, 'Hot', 'Warm')) weather_type FROM Weather w JOIN Countries c ON c.country_id = w.country_id WHERE DATE_FORMAT(day, '%Y-%m') = '2019-11' GROUP BY w.country_id