joining two tables by value of one column and calculating - sql

Question

Thank you for interested in question.
I have in one table some thing like this
sifrez | sifKorisnikPK | Status
1 | 1 | 'P'
2 | 1 | 'P'
3 | 1 | 'U'
4 | 2 | 'P'
5 | 2 | 'P'
6 | 2 | 'U'
7 | 2 | 'U'
8 | 3 | 'U'
9 | 3 | 'U'
10 | 3 | 'U'
11 | 3 | 'U'
12 | 4 | 'P'
13 | 4 | 'P'
Then i created stored function which count values of P and U search ratio between them find user with that id and return username
CREATE PROCEDURE sp_getBestUsernames
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for procedure here
SELECT SifKorisnikPK, COUNT (Status) AS BrojLosih
INTO #LosaRez
FROM Rezervacija
WHERE Status = 'P'
GROUP BY SifKorisnikPK
order by count(*) desc
After this part it give me
sifKorisnikPK | BrojLosih
1 | 2
2 | 2
4 | 2
This only count p on status.
And this:
SELECT SifKorisnikPK, COUNT (Status) AS BrojDobrih
INTO #DobraRez
FROM Rezervacija
WHERE Status = 'U'
GROUP BY SifKorisnikPK
order by count(*) desc
i get
sifKorisnikPK | BrojDobrih
1 | 1
2 | 2
3 | 4
Only count U. This part work like a charm...
And here i try to join this two temp tables and calculate ratio and return SifKorisnik with best ratio
SELECT Username FROM Korisnik
WHERE SifKorisnik = (SELECT TOP 1 a.SifKorisnikPK
FROM #DobraRez a
INNER JOIN #LosaRez b
ON a.SifKorisnikPK = b.SifKorisnikPK OR
a.SifKorisnikPK != b.SifKorisnikPK
WHERE a.BrojDobrih - b.BrojLosih > 0
ORDER BY a.BrojDobrih - b.BrojLosih )
END
And after joining operation i expect to get some thing like this, which i'm not getting
sifKorisnikPK | BrojDobrih | BrojLosih
1 | 1 | 2
2 | 2 | 2
3 | 4 | 0
4 | 0 | 2
so i can calculate the ratio BrojDobrih - BrojLosih and return the SifKorisnikPK which is the best ratio. In this case it would be SifKorisnik 3.
But my procedure get SifKorisnik 2 which is second best. I presume that the problem is in joining operation that it doesn't input 0. So how can i solve this?

Answer 1

Try this:
SELECT
A.sifKorisnikPK,
IsNull(BrojDobrih,0) BrojDobrih,
IsNull(BrojLosih,0) BrojLosih
FROM (select distinct sifKorisnikPK from Rezervacija) A
LEFT JOIN #LosaRez B
ON A.sifKorisnikPK = B.sifKorisnikPK
LEFT JOIN #DobraRez C
ON A.sifKorisnikPK = C.sifKorisnikPK
ORDER BY (IsNull(BrojDobrih,0) - IsNull(BrojLosih,0))