题目：
题解：

--这道题主要考察中位数的取法
SELECT 
category_id,cast(sum(price)/count(1) as DECIMAL(16,2)) medprice
from(
SELECT
  category_id,
  price,
  rn,
  max(rn)over(partition by category_id) max_rn
from
  (
    SELECT
      category_id,
      price,
      row_number() over (
        partition by
          category_id
        order by
          price
      ) rn
    from
      sku_info
  ) t
)t
where
--ceil(3.1415, 2)-->4 ; floor(3.1415, 2)-->3
--ceil 向上取整，奇数取中位数，偶数取靠右侧的位置；floor向下取整，奇数同上，偶数取靠左侧的位置
  rn in (ceil((max_rn+1)/2),floor((max_rn+1)/2))
  group by category_id;