Running multiple subqueries

Question

I am pulling one code (ICD9) which is in table AbsDrgDiagnosis.Diagnosis. I need to pull another code (SNOMED_CT) which is in another table DMisNomenclatureMapCodes.CodeID when DMisNomenclatureMapCodes.CodeSetID = 'SNOMED_CT'

Then only way to link these two tables is by AbsDrgDiagnosis.Diagnosis = DMisNomenclatureMapCodes.CodeID when DMisNomenclatureMapCodes.CodeSetID = 'ICD9'

So for example I have to report 3942005 from DMisNomenclatureMapCodes.CodeID when CodeSetID = 'SNOMED_CT'.

EXAMPLE DATA:
                                Diagnosis   
AbsDrgDiagnosis                 290.23  

                                CodeID         CodeSetID    MisNomenclatureMapID
DMisNomenclatureMapCodes        290.23         ICD9         IMO-PROC-99959
                                3942005        SNOMED_CT    IMO-PROC-99959
                                53899          CPT          IMO-PROC-99959

So far I can only compare AbsDrgDiagnosis.Diagnosis on DMisNomenclatureMapCodes.CodeID, which both equal 290.23, but after that I am lost as to how I get the SNOMED code. I assume I have to do another subquery on DMisNomenclatureMapCodes.MisNomenclatureMapID to get the grouping and then find the CodeSetID of SNOMED_CT to get the final value of CodeID 3942005. how do I attempt this? Any help would be greatly appreciated, I tried a couple of subqueries but they errored out. I am new to SQL so if I didnt say something correctly or write it in expert fashion please be kind.

CODE:
DECLARE
    SET @StartDate = '10/28/2013 00:00:000'
    SET @EndDate = '12/28/2013 23:59:000'

SELECT 
    ,Diagnosis AS Code_3
    ,DMisNomenclatureMapCodes.CodeID
    ,DMisNomenclatureMapCodes.MisNomenclatureMapID

FROM AbsDrgDiagnoses

    LEFT JOIN AbstractData
    ON AbstractData.VisitID = AbsDrgDiagnoses.VisitID
    LEFT JOIN DMisNomenclatureMapCodes
    ON DMisNomenclatureMapCodes.CodeID = AbsDrgDiagnoses.Diagnosis

WHERE AbstractData.DischargeDateTime BETWEEN @StartDate and @EndDate

Answer 1

Thanks to anyone who replied to this. As it turns out I had to build a couple of sub-queries to achieve what I wanted. The bottom most sub-query returns the nomenclature map results when both ICD9 codes are present via

NMC.CodeID = AbsDrgDiagnoses.Diagnosis. 

Now this was my problem, I didn't know that you could include an AND statement within the sub-query when it was returning a single result from another sub-query, learned something new! Thus I could only return the CodeSetID of 'SNOMED_CT' and not the actual CodeID of 5510009. By putting in

WHERE NMC.CodeSetID = 'SNOMED_CT' AND NMC.MisNomenclatureMapID IN

I was then able to return the value needed.

CODE:

,COALESCE((SELECT NMC.CodeID
    FROM DMisNomenclatureMapCodes NMC   
    WHERE NMC.CodeSetID = 'SNOMED_CT'  AND NMC.MisNomenclatureMapID IN
    (SELECT NMC.MisNomenclatureMapID 
        FROM DMisNomenclatureMapCodes NMC   
        WHERE (NMC.CodeID = AbsDrgDiagnoses.Diagnosis)
    ) 
),'') AS SNOSet_TEST

Answer 2

Given this, "Then only way to link these two tables is by AbsDrgDiagnosis.Diagnosis = DMisNomenclatureMapCodes.CodeID when DMisNomenclatureMapCodes.CodeSetID = 'ICD9'", couldn't you just change this:

LEFT JOIN DMisNomenclatureMapCodes
ON DMisNomenclatureMapCodes.CodeID = AbsDrgDiagnoses.Diagnosis

to this:

LEFT JOIN DMisNomenclatureMapCodes
ON DMisNomenclatureMapCodes.CodeID = AbsDrgDiagnoses.Diagnosis
and DMisNomenclatureMapCodes.CodeSetID = 'ICD9'

?