Multiple MAX values select using inner join - sql

Question

I have query that work for me only when values in the StakeValue don't repeat.
Basically, I need to select maximum values from SI_STAKES table with their relations from two other tables grouped by internal type.
SELECT a.StakeValue, b.[StakeName], c.[ProviderName]
FROM SI_STAKES AS a
INNER JOIN SI_STAKESTYPES AS b ON a.[StakeTypeID] = b.[ID]
INNER JOIN SI_PROVIDERS AS c ON a.[ProviderID] = c.[ID] WHERE a.[EventID]=6
AND a.[StakeGroupTypeID]=1
AND a.StakeValue IN
(SELECT MAX(d.StakeValue) FROM SI_STAKES AS d
WHERE d.[EventID]=a.[EventID] AND d.[StakeGroupTypeID]=a.[StakeGroupTypeID]
GROUP BY d.[StakeTypeID])
ORDER BY b.[StakeName], a.[StakeValue] DESC
Results for example must be:
[ID] [MaxValue] [StakeTypeID] [ProviderName]
1 1,5 6 provider1
2 3,75 7 provider2
3 7,6 8 provider3
Thank you for your help

Answer 1

There are two problems to solve here.
1) Finding the max values per type. This will get the Max value per StakeType and make sure that we do the exercise only for the wanted events and group type.
SELECT StakeGroupTypeID, EventID, StakeTypeID, MAX(StakeValue) AS MaxStakeValue
FROM SI_STAKES
WHERE Stake.[EventID]=6
AND Stake.[StakeGroupTypeID]=1
GROUP BY StakeGroupTypeID, EventID, StakeTypeID
2) Then we need to get only one return back for that value since it may be present more then once.
Using the Max Value, we must find a unique row for each I usually do this by getting the Max ID is has the added advantage of getting me the most recent entry.
SELECT MAX(SMaxID.ID) AS ID
FROM SI_STAKES AS SMaxID
INNER JOIN (
SELECT StakeGroupTypeID, EventID, StakeTypeID, MAX(StakeValue) AS MaxStakeValue
FROM SI_STAKES
WHERE Stake.[EventID]=6
AND Stake.[StakeGroupTypeID]=1
GROUP BY StakeGroupTypeID, EventID, StakeTypeID
) AS SMaxVal ON SMaxID.StakeTypeID = SMaxVal.StakeTypeID
AND SMaxID.StakeValue = SMaxVal.MaxStakeValue
AND SMaxID.EventID = SMaxVal.EventID
AND SMaxID.StakeGroupTypeID = SMaxVal.StakeGroupTypeID
3) Now that we have the ID's of the rows that we want, we can just get that information.
SELECT Stakes.ID, Stakes.StakeValue, SType.StakeName, SProv.ProviderName
FROM SI_STAKES AS Stakes
INNER JOIN SI_STAKESTYPES AS SType ON Stake.[StakeTypeID] = SType.[ID]
INNER JOIN SI_PROVIDERS AS SProv ON Stake.[ProviderID] = SProv.[ID]
WHERE Stake.ID IN (
SELECT MAX(SMaxID.ID) AS ID
FROM SI_STAKES AS SMaxID
INNER JOIN (
SELECT StakeGroupTypeID, EventID, StakeTypeID, MAX(StakeValue) AS MaxStakeValue
FROM SI_STAKES
WHERE Stake.[EventID]=6
AND Stake.[StakeGroupTypeID]=1
GROUP BY StakeGroupTypeID, EventID, StakeTypeID
) AS SMaxVal ON SMaxID.StakeTypeID = SMaxVal.StakeTypeID
AND SMaxID.StakeValue = SMaxVal.MaxStakeValue
AND SMaxID.EventID = SMaxVal.EventID
AND SMaxID.StakeGroupTypeID = SMaxVal.StakeGroupTypeID
)

Answer 2

You can use the over clause since you're using T-SQL (hopefully 2005+):
select distinct
a.stakevalue,
max(a.stakevalue) over (partition by a.staketypeid) as maxvalue,
b.staketypeid,
c.providername
from
si_stakes a
inner join si_stakestypes b on
a.staketypeid = b.id
inner join si_providers c on
a.providerid = c.id
where
a.eventid = 6
and a.stakegrouptypeid = 1
Essentially, this will find the max a.stakevalue for each a.staketypeid. Using a distinct will return one and only one row. Now, if you wanted to include the min a.id along with it, you could use row_number to accomplish this:
select
s.id,
s.maxvalue,
s.staketypeid,
s.providername
from (
select
row_number() over (order by a.stakevalue desc
partition by a.staketypeid) as rownum,
a.id,
a.stakevalue as maxvalue,
b.staketypeid,
c.providername
from
si_stakes a
inner join si_stakestypes b on
a.staketypeid = b.id
inner join si_providers c on
a.providerid = c.id
where
a.eventid = 6
and a.stakegrouptypeid = 1
) s
where
s.rownum = 1