分组前80％的类别

问题描述

我需要SQL查询进行分组，这些分类只包含那些总共包含至少80％所有类别的组，其他罕见类别（包含总数的20％）应该表示为其他

因此，按分类颜色对苹果进行分组的查询结果应该如下所示：

  RED 1118 44％）
黄色711 28％>至少80％
绿色229 9％）
其他482 19％
  

如何做到这一点？

解决方案

我会用聚合和分析功能的组合来做到这一点。当稀有物的累积总和低于20％时，颜色被放入其他类别：

  select（case when cumcntdesc  else color 
 end）as color，sum（cnt）as cnt 
 from（select color，count（*）as cnt，$ b $作为cumcntdesc，
 sum（count（*））over（）的总数（count（*））over（count by（*）asc）as totalcnt 
 from t 
 group by color 
）t 
 group by（cumcntdesc< totalcnt * 0.2 then then'other'
 else color 
 end）
  pre> 
 
 
 是一个SQL小提琴。
 
I need SQL query for grouping by some category which would present quantities of only those groups which in total contain at least 80% of all categories, other rare categories (containing up to 20% of total) should be represented like "other".

So the result of such a query for grouping apples by category color should look like this:
RED    1118 44% )
YELLOW  711 28% > at least 80%
GREEN   229  9% )
other   482 19%
How to do that?
 解决方案 
I would do this with a combination of aggregation and analytic functions.  The colors are put in the "other" category when the cumulative sum of the rarest is under 20%:
select (case when cumcntdesc < totalcnt * 0.2 then 'other'
             else color
        end) as color, sum(cnt) as cnt
from (select color, count(*) as cnt,
             sum(count(*)) over (order by count(*) asc) as cumcntdesc,
             sum(count(*)) over () as totalcnt
      from t
      group by color
     ) t
group by (case when cumcntdesc < totalcnt * 0.2 then 'other'
               else color
          end)
Here is a SQL Fiddle.
                        
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