#中位数(题目四的答案) SELECT job, ROUND(CASE WHEN num % 2 = 1 THEN (num + 1) / 2 ELSE num / 2 END,0) "start" , ROUND(CASE WHEN num % 2 = 1 THEN (num + 1) / 2 ELSE num / 2 + 1 END,0) "end" FROM (SELECT job, COUNT(job) num FROM grade GROUP BY job) t ORDER BY job #排名(题目二的答案) SELECT id, job, score, dense_rank(...