How to aggregate and make a ratio between two fields from a CTE - sql

Question

I have a query which return a flag wheter a client who made a contract with my company this year is new or returning:
WITH Resultset AS(
SELECT
Cnt = COUNT(*)
,KliRC --personal identification number
FROM dbo.Smlouvy
WHERE VyplacenaCastka > 0
GROUP BY KliRC
)
SELECT
s.KliRC
,CASE WHEN Cnt > 1 THEN 1 ELSE 0 END AS Novy --new client
,CASE WHEN Cnt = 1 THEN 1 ELSE 0 END AS Stavajici --existing client
FROM Resultset JOIN dbo.Smlouvy s ON s.KliRC = resultset.KliRC
WHERE (YEAR(DatumZadosti) = YEAR(GETDATE())) AND (s.KliRC NOT LIKE '%x')
Now, I need to aggregate all the new and existing clients and make a ratio between them.
Any ideas? Thanks in advance.

Answer 1

I think this does what you want:
WITH Resultset AS (
SELECT COUNT(*) as cnt,
KliRC --personal identification number,
(CASE WHEN COUNT(*) > 1 THEN 1 ELSE 0 END) AS Novy --new client
(CASE WHEN COUNT(*) = 1 THEN 1 ELSE 0 END) AS Stavajici
FROM dbo.Smlouvy
WHERE VyplacenaCastka > 0
GROUP BY KliRC
)
SELECT SUM(Novy) / SUM(Stavajici)
FROM Resultset r JOIN
dbo.Smlouvy s
ON s.KliRC = r.KliRC
WHERE YEAR(DatumZadosti) = YEAR(GETDATE()) AND
s.KliRC NOT LIKE '%x';

Answer 2

Your query can be simplified to
SELECT SUM(Novy)*1.0/SUM(Stavajici)
FROM (
SELECT KliRC
,CASE WHEN COUNT(*) OVER(PARTITION BY KliRC) > 1 THEN 1 ELSE 0 END AS Novy --new client
,CASE WHEN COUNT(*) OVER(PARTITION BY KliRC) = 1 THEN 1 ELSE 0 END AS Stavajici --existing client
FROM dbo.Smlouvy
WHERE YEAR(DatumZadosti) = YEAR(GETDATE()) AND KliRC NOT LIKE '%x'
) T