SQL - OutterApply and Left Join - mysql

Question

I'm working with a large stored procedure, I'm having trouble with a small portion of it.
When I execute a query on the table im joining, there can be 0, 1 or 2 results. If there are 0 results, I don't really care, my code returns null values, no big deal. If there is 1 result, my code returns the correct values, however, if there are 2 results, I am having trouble selecting the second result.
My code below works until the second OutterApply(the AHM2 stuff). Does anyone see what I am doing wrong?
The animal ID is identical for both OuterApplys. I just need to return the second result, if there is one, and if it is not the same as the first one.
SELECT TOP 1
AHM.AnimalHerdManagementId,
AHM.HerdManagementId,
AHM2.AnimalHerdManagementId,
AHM2.HerdManagementId,
HM.Code AS HerdManagementCode,
HM2.Code AS HerdManagementCode2
OUTER APPLY
(
SELECT TOP 1 AHM.AnimalHerdManagementId, AHM.HerdManagementId
FROM dbo.AnimalHerdManagement AHM
WHERE AHM.AnimalId = A.AnimalId AND ISNULL(AHM.EffectiveFrom, #EffectiveFrom) <= #EffectiveFrom
ORDER BY AHM.EffectiveFrom DESC
) AHM
LEFT JOIN dbo.HerdManagement HM ON AHM.HerdManagementId = HM.HerdManagementId
OUTER APPLY
(
SELECT TOP 1 AHM2.AnimalHerdManagementId, AHM2.HerdManagementId
FROM dbo.AnimalHerdManagement AHM2
WHERE AHM2.AnimalId = A.AnimalId AND AHM2.AnimalHerdManagementId != AHM.AnimalHerdManagementId AND ISNULL(AHM2.EffectiveFrom, #EffectiveFrom) <= #EffectiveFrom
ORDER BY AHM2.EffectiveFrom DESC
) AHM2
LEFT JOIN dbo.HerdManagement HM2 ON AHM2.HerdManagementId = HM2.HerdManagementId

Answer 1

I think I can help you with the OUTER APPLY but the method of getting the two different values is going to need some help as my solution is a total hack.
First, you don't need to join on the outer apply. The join is implied. So you can completely eliminate the join syntax from your query.
Second, AnimalHerdManagement looks/seems like a special table called a Junction Table. All the data contained in it is contained elsewhere (That it contains completely redundant data is why it's called a special table). But that is minor.
Finally, here is some example code I threw together that accomplishes what you are after. The method I am using to retrieve different results on the two outer apply's is a hack, but if you are sure that will always be true, it might work. I am not able to get a multi-level outer apply to work.
select * from AH_Animal A
outer apply
(
select max (HerdManagementID) as HerdMgmtID1 from AH_AnimalHerdManagement HM1 where HM1.AnimalID = A.AnimalID
) as z
outer apply
(
select min (HerdManagementID) as HerdMgmtID2 from AH_AnimalHerdManagement HM2 where HM2.AnimalID = A.AnimalID
) as zz
I hope that helped. There has to be another solution to this, as this would not work at all if you ever expected 3 results.
Query Results: