Get percentages of larger group - sql

Question

The query below is kind of an ugly one so I hope I've got it spaced well enough to make it readable. The query finds the percentage of people that visit a given hospital if they are from a certain area. For instance, if 100 people live in county X and 20 go to hospital A and 80 go to hospital B the query outputs. How the heck is this sort of thing done? Let me know if I need to document the query or whatever I can do to make it clearer.
hospital A 20
hospital B 80
The query below works exactly like I want it to, but it give me thinking: how could this be done for every county in my table?
select hospitalname, round(cast(counts as float)/cast(fayettestrokepop as float)*100,2)as percentSeen
from
(
SELECT tblHospitals.hospitalname, COUNT(tblHospitals.hospitalname) AS counts, tblStateCounties_1.countyName,
(SELECT COUNT(*) AS Expr1
FROM Patient INNER JOIN
tblStateCounties ON Patient.stateCode = tblStateCounties.stateCode AND Patient.countyCode = tblStateCounties.countyCode
WHERE (tblStateCounties.stateCode = '21') AND (tblStateCounties.countyName = 'fayette')) AS fayetteStrokePop
FROM Patient AS Patient_1 INNER JOIN
tblHospitals ON Patient_1.hospitalnpi = tblHospitals.hospitalnpi INNER JOIN
tblStateCounties AS tblStateCounties_1 ON Patient_1.stateCode = tblStateCounties_1.stateCode AND Patient_1.countyCode = tblStateCounties_1.countyCode
WHERE (tblStateCounties_1.stateCode = '21') AND (tblStateCounties_1.countyName = 'fayette')
GROUP BY tblHospitals.hospitalname, tblStateCounties_1.countyName
) as t
order by percentSeen desc
EDIT: sample data
The sample data below is without the outermost query (the as t order by part).
The countsInTheCounty column is the (select count(*)..) part after 'tblStateCounties_1.countyName'
hospitalName hospitalCounts countyName countsInTheCounty
st. james 23 X 300
st. jude 40 X 300
Now with the outer query we would get
st james 0.076 (23/300)
st. jude 0.1333 (40/300)

Answer 1

Here is my guess. You'll have to test against your data or provide proper DDL + sample data.
;WITH totalCounts AS
(
SELECT StateCode, countyCode, COUNT(*) AS totalcount
FROM dbo.Patient GROUP BY StateCode, countyCode
)
SELECT
h.hospitalName,
hospitalCounts = COUNT(p.hospitalnpi),
c.countyName,
countsInTheCounty = tc.totalCount,
percentseen = CONVERT(DECIMAL(5,2), COUNT(p.hospitalnpi)*100.0/tc.totalCount)
FROM
dbo.Patient AS p
INNER JOIN
dbo.tblHospitals AS h
ON p.hospitalnpi = h.hospitalnpi
INNER JOIN
totalCounts AS tc
ON p.StateCode = tc.StateCode
AND p.countyCode = tc.countyCode
INNER JOIN
dbo.tblStateCounties AS c
ON tc.StateCode = c.stateCode
AND tc.countyCode = c.countyCode
GROUP BY
h.hospitalname,
c.countyName,
tc.totalcount
ORDER BY
c.countyName,
percentseen DESC;