SQL中位数

表：sku_info
字段：sku_id name category_id price

需求：求各分类商品的价格中位数

期望结果：
category_id medprice

select 
        category_id
        ,cast(avg(if(ct/2 = 0,if(num = ct / 2  or num = ct / 2 + 1, price, null ),if(num = ct / 2  + 1, price, null ))) ) as decimal(16,2)
 
 from (
    select category_id,price,row_number() over(partition by category_id order by price) num
     ,count(*) over(partition by category_id) ct from sku_info 
) a group by category_id