外部查询和子查询中使用的COUNT和GROUP函数

Question

我编写了一个查询，其中涉及创建汇总表和保存在单个表上的值的百分比（转储到一行）。 每个子查询在WHERE参数方面略有不同。 例如：

select distinct
count(KS2_PupilMatchingRefAnonymous) AS 'Total Pupils',

    (select count(KS2_PupilMatchingRefAnonymous) 
        from KS2_CandInd_2011 
        where KS2_MMSCH=1 
        and KS2_ELIGENGTA=1) AS 'All Eligible Pupils',
    (select count(*) 
        from KS2_CandInd_2011 
        where KS2_MMSCH=1 
        and KS2_ELIGENGTA=1 
        and KS2_ELIGENGTA=1 
        and FSMeligible=1) AS 'Eligible FSM only',  
    (select round(
    (cast((
        select count(*) 
            from KS2_CandInd_2011 
            where KS2_MMSCH=1 
            and KS2_ELIGENGTA=1 
            and KS2_ELIGENGTA=1 
            and FSMeligible=1) AS float) / 
    cast((
        select count(KS2_PupilMatchingRefAnonymous) 
            from KS2_CandInd_2011 
            where KS2_MMSCH=1 
            and KS2_ELIGENGTA=1) AS float))*100,2
             )) AS '% Eligible FSM'
from KS2_CandInd_2011
where KS2_MMSCH=1

我现在想根据性别用COUNT（当然还有GROUP BY）细分每个子查询。 如果将性别的COUNT / GROUP BY放在外部查询中，则仅会获得“总学生”值的细分/拆分。

如果我尝试在子查询中输入相同的条款

消息116，级别16，状态1，行12当未将EXISTS引入子查询时，只能在选择列表中指定一个表达式。

根据相关子查询，内部查询并未真正引用外部查询，因此尽管我已尽力而为，但我不确定如何克服该错误。 有没有人有什么建议？

Answer 1

我们可以用如下所示的更简单的方式重写查询。（假设您的表中有一个名为“ gender ”的列： KS2_CandInd_2011

select 
a.gender
,count(*) AS 'Total Pupils',
,sum(case 
         when KS2_MMSCH=1 and  KS2_ELIGENGTA=1 then  1
       else 0
    end
    ) as  'All Eligible Pupils'
,sum(case
    when KS2_MMSCH=1 and KS2_ELIGENGTA=1 and KS2_ELIGENGTA=1 and FSMeligible=1 then 1
      else 0
    end) as  'Eligible FSM only'
,round(cast( sum(case 
                    when KS2_MMSCH=1 and  KS2_ELIGENGTA=1 then  1
                  else 0
                end
            ) as float)/

cast(sum(case
    when KS2_MMSCH=1 and KS2_ELIGENGTA=1 and KS2_ELIGENGTA=1 and FSMeligible=1 then 1
      else 0
    end)  as float)
        *100,2)  AS '% Eligible FSM'
from KS2_CandInd_2011 as a
where a.KS2_MMSCH=1
group by a.gender
order by a.gender;

我相信以下内容将为您提供原始查询的确切输出：

    select 
   ,count(*) AS 'Total Pupils',
    ,sum(case 
             when KS2_MMSCH=1 and  KS2_ELIGENGTA=1 then  1
           else 0
        end
        ) as  'All Eligible Pupils'
    ,sum(case
        when KS2_MMSCH=1 and KS2_ELIGENGTA=1 and KS2_ELIGENGTA=1 and FSMeligible=1 then 1
          else 0
        end) as  'Eligible FSM only'
    ,round(cast( sum(case 
                        when KS2_MMSCH=1 and  KS2_ELIGENGTA=1 then  1
                      else 0
                    end
                ) as float)/

    cast(sum(case
        when KS2_MMSCH=1 and KS2_ELIGENGTA=1 and KS2_ELIGENGTA=1 and FSMeligible=1 then 1
          else 0
        end)  as float)
            *100,2)  AS '% Eligible FSM'
    from KS2_CandInd_2011 as a
    where a.KS2_MMSCH=1
;