题解 | 窗口函数求解
最差是第几名(二)
http://www.nowcoder.com/practice/165d88474d434597bcd2af8bf72b24f1
SELECT grade
FROM
(
SELECT grade,
SUM(number) OVER(ORDER BY grade) AS rk1,#累计求和正序排序
SUM(number) OVER(ORDER BY grade DESC) AS rk2,#累计求和倒序排序
SUM(number) OVER() AS total #求人数的最大值
FROM class_grade
ORDER BY grade
) AS t
WHERE rk1 >= total/2
AND rk2 >= total/2
ORDER BY grade