执行数学运算以从 COUNT 和 GROUP BY 语句输出

Question

假设我有一个 Yes/No 数据列。然后我可以通过

计算每个结果类别中的观察结果

Select MyVar, count(MyVar) from MyTable
group by MyVaR;

输出类似于：

MyVar    count(MyVar)
Yes               10
No                5

如何向此输出添加另一个元素table，这是分数 (Yes/No) 所以我的最终 table 类似于：

MyVar    count(MyVar)
Yes               10
No                5
Fraction          2

有没有简单的解决方法？

Answer 1

这是最简单的 -- 在这种格式下 -- 使用 union all:

with t as (
      Select MyVar, count(MyVar) as cnt
      from MyTable
      group by MyVaR
     )
select MyVar
from t
union all
select 'Ratio', sum(case when MyVar = 'Yes' then cnt else 0 end) / sum(case when MyVar = 'No' then cnt else 0 end)
from t;

也就是说，我会使用条件聚合并将所有值放在一行中：

select sum(case when MyVar = 'Yes' then cnt else 0 end) as yes,
       sum(case when MyVar = 'Yes' then cnt else 0 end) as no,
       sum(case when MyVar = 'Yes' then cnt else 0 end) / sum(case when MyVar = 'No' then cnt else 0 end) as ratio
from t;

Answer 2

你可以使用 group by grouping sets()：

Select 
   case 
      when grouping(MyVar)=0 then MyVar
      else 'Fraction'
   end grouping_value,
   case 
      when grouping(MyVar)=0 then count(MyVar) 
      else count(decode(MyVar,'Yes',1)) / count(decode(MyVar,'No',1))
   end c
from MyTable
group by grouping sets(MyVaR,())

带有示例数据的完整测试用例：

with MyTable(MyVar) as (
  select * 
  from table(sys.odcivarchar2list(
               'Yes','Yes','Yes','Yes','Yes','Yes','Yes','Yes','Yes','Yes',
               'No','No','No','No','No'
            ))
)
Select 
   case 
      when grouping(MyVar)=0 then MyVar
      else 'Fraction'
   end grouping_value,
   case 
      when grouping(MyVar)=0 then count(MyVar) 
      else count(decode(MyVar,'Yes',1)) / count(decode(MyVar,'No',1))
   end val
from MyTable
group by grouping sets(MyVaR,())
;

结果：

GROUPING_VALUE         VAL
--------------- ----------
No                       5
Yes                     10
Fraction                 2

执行数学运算以从 COUNT 和 GROUP BY 语句输出

Do math operations to output from COUNT and GROUP BY statemetns

sql

oracle

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