SQL Query combine multiple results or Join tables - sql-server

Question

I have the Following tables
Disposition Table
Dis_ID | OfferID | RequestID
------------------------------------
34564 | 123 | 9
77456 | 123 | 8
25252 | 124 | 7
46464 | 125 | 10
36464 | 125 | 6
35353 | 125 | 5
Request Table
RequestID | AccountNum |
---------------------------
5 | 548543 |
6 | 548543 |
7 | 684567 |
8 | 684567 |
9 | 684567 |
10 | 548543 |
11 | 684567 |
Rank Table
RankID | OfferId | RequestID | Score
-------------------------------------------
34564 | 123 | 11 | 1
77456 | 124 | 11 | 2
25252 | 125 | 11 | 3
Using the data above I need a query which would behave as follows given a request number look at every record in the Rank Table in this example we have 3 (123, 124, & 125). return the OfferId that appears the fewest times in the Disposition table for this joined account number. in this example offerId 123 appears twice for this account number, offerId 124 appears once and offerId 125 doesn't appears at all for this account number. So offerId 125 should be returned. The offerId which exist in the Rank Table with the fewest appearances in the Disposition table should always be returned unless they are all the same then return the offerId with the lowest value in the Score field. for example if none of the offerIDs appeared in the Dispostion table offerId 123 would return since its Score value is 1.
Resulting table would look something like this
| OfferId | Score | Dis_Occurrences
---------------------------------------------------------------
| 123 | 1 | 2
| 124 | 2 | 1
| 125 | 3 | 0 <--Return this record
This is what I have so far.
SELECT oRank.OfferId, oRank.Rank_Number, count(oRank.OfferId) AS NumDispositions
From Rank oRank
join Request req
on oRank.RequestId = req.RequestId
join Disposition dis
on oRank.OfferId = dis.OfferId
where req.Customer_Account_Number = 684567 and req.RequestId = 11 and oRank.OfferId = dis.OfferId
group by oRank.Rank_Number, oRank.OfferId
order by NumDispositions, oRank.Rank_Number
My incorrect Resulting table looks like this
| OfferId | Score | Dis_Occurrences
---------------------------------------------------------------
| 123 | 1 | 2
| 124 | 2 | 1
| 125 | 3 | 3
It is counting the total number of times the offerId appears in the Disposition Table

Answer 1

EDIT - based on author's comments, here's another version:
Example in SQLFiddle: http://sqlfiddle.com/#!6/d3f99/1/0
with RankReqMap as (
select rnk.OfferId, rnk.Score, reqAcct.AccountNum, reqReq.RequestID
from [Rank] rnk
left join Request reqAcct on reqAcct.RequestID = rnk.RequestID
left join Request reqReq on reqReq.AccountNum = reqAcct.AccountNum
where rnk.RequestID = 11 -- Put your RequestId filter here
)
select oRank.OfferId
,oRank.Score
,count(dis.RequestID) as NumDispositions
from RankReqMap oRank
left join Disposition dis on dis.OfferID = oRank.OfferId
and dis.RequestID = oRank.RequestID
group by oRank.OfferId , oRank.Score
order by NumDispositions, oRank.Score;
ORIGINAL POST
Example in SQLFiddle: http://sqlfiddle.com/#!6/770a8/1/0
This query makes the assumption that you're joining Disposition to Rank based on OfferID, since the RequestIDs for those tables in your example data don't match up. You may have to tweak depending on your needs, but something like the query below should get you the record you're looking for:
-- Gather base data
with RankData as (
select rnk.RankID
,rnk.OfferID
,rnk.RequestID
,rnk.Score
,Dis_Occurrences = count(dis.OfferID)
from dbo.[Rank] rnk
left join dbo.Disposition dis on dis.OfferID = rnk.OfferId
left join dbo.Request req on req.RequestID = rnk.RequestID
group by rnk.RankID, rnk.OfferID, rnk.RequestID, rnk.Score
)
-- Rank count of Dis_Occurrences, taking lowest score into account as a tie breaker
, DispRanking as (
select rdt.*, Dis_Rank = row_number() over (order by Dis_Occurrences asc, rdt.Score asc)
from RankData rdt
)
-- Return only the value with the highest ranking
select * from DispRanking where Dis_Rank = 1
Note also that if you convert the second CTE into a naked SELECT and remove the SELECT statement at the end, you can see all of the records and how they get ranked by the row_number() function:
-- Gather base data
with RankData as (
select rnk.RankID
,rnk.OfferID
,rnk.RequestID
,rnk.Score
,Dis_Occurrences = count(dis.OfferID)
from dbo.[Rank] rnk
left join dbo.Disposition dis on dis.OfferID = rnk.OfferId
left join dbo.Request req on req.RequestID = rnk.RequestID
group by rnk.RankID, rnk.OfferID, rnk.RequestID, rnk.Score
)
-- Output all values, with rankings
select rdt.*, Dis_Rank = row_number() over (order by Dis_Occurrences asc, rdt.Score asc)
from RankData rdt
Good luck!

Answer 2

I think you can use window function for this:
;with disp as(select offerid, count(*) as ocount
from dispositions group by offerid),
rnk as(select r.offerid,
row_number() over(partition by r.requestid
order by isnull(d.ocount, 0), r.score) rn
from ranks r
left join disp d on r.offerid = d.offerid)
select * from rnk where rn = 1