COUNT and GROUP functions used in outer query and subquery - sql

Question

I have written a query which involves creating sum figures and percentages of values (dumped to a single row) held on a single table. Each of the subqueries varies slightly with regard to the WHERE parameters. For example:
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
I now want breakdown each subquery with a COUNT (and GROUP BY, of course) according to gender. If the COUNT/GROUP BY for gender is placed in the outer query, I only get a breakdown/split for the 'Total Pupils' value.
If I try to enter the same clauses in the subqueries I am told
Msg 116, Level 16, State 1, Line 12
Only one expression can be specified in the select list when the subquery is not introduced with EXISTS.
The inner queries aren't really referencing the outer query, as per a correlated subquery, so im not really sure how to overcome the error despite my best attempts. Does anyone have any suggestions?

Answer 1

We can re-write your query in much simpler way as shown below.(assuming you have a column called gender in your table: 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;
The following is I believe will give you the exact output of your original query:
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
;