Counting average from two queries - mysql

Question

I'm trying get the average from two select queries. In the first select i'm counting all "votes" per district, now i want to devide it by total sum of votes in voivodeship(It can have more than one district)
select void.name, d.name, t.name, COUNT(v.idvotes) as "Percent of votes"
from voivodeship void, politicialteam t, votes v, candidates c, person p, district d
where c.idcandidates = v.idcandidates
and p.idperson = c.idperson
and c.idpoliticialteam = t.idpoliticialteam
and void.idvoivodeship = d.idvoivodeship
and c.iddistrict = d.iddistrict
GROUP by d.name ORDER by void.name ASC
SELECT Count(vo.idvotes)
from votes vo, candidates c, district d, voivodeship v
where d.idvoivodeship = v.idvoivodeship
and d.iddistrict = c.iddistrict
and vo.idcandidates = c.idcandidates
GROUP by v.name
Total for "dolnośląskie": 119987
In my example i want merge this two queries to get result 40038/119987, 40078/119987 etc..

Answer 1

You can achieve this result in two different way, depending on your DBMS.
If your DBMS supports Extended SQL queries, you should try to get a partition on void.name and aggregate the result in order to compute your percentage:
SELECT void.name,
d.name,
t.name,
COUNT(v.idvotes) as "Percent of votes",
COUNT(v.idvotes)/SUM(COUNT(v.idvoted))*100 OVER (PARTITION BY void.name) as "Votes percentage"
FROM voivodeship void, politicialteam t, votes v, candidates c, person p, district d
where c.idcandidates = v.idcandidates and
p.idperson = c.idperson and
c.idpoliticialteam = t.idpoliticialteam and
void.idvoivodeship = d.idvoivodeship and
c.iddistrict = d.iddistrict
GROUP BY d.name, void.name
ORDER BY void.name ASC
If your DBMS does not support Extended SQL, you can achieve the same result nesting the two queries:
SELECT void.name,
d.name,
t.name,
COUNT(v.idvotes) as "Percent of votes",
COUNT(v.idvotes)/(
SELECT Count(vo.idvotes)
FROM votes vo1, candidates c1, district d1, voivodeship v1
WHERE d1.idvoivodeship = v1.idvoivodeship and
d1.iddistrict = c1.iddistrict and
vo1.idcandidates = c1.idcandidates and
d1.name = d.name
GROUP BY v.name
)*100 AS "Percentage of votes"
FROM voivodeship void, politicialteam t, votes v, candidates c, person p, district d
where c.idcandidates = v.idcandidates and
p.idperson = c.idperson and
c.idpoliticialteam = t.idpoliticialteam and
void.idvoivodeship = d.idvoivodeship and
c.iddistrict = d.iddistrict
GROUP BY d.name, void.name
ORDER BY void.name ASC
N.B. In the last solution you can merge the queries adding another JOIN condition on the nested query such as
d1.name = d.name