如果第一个值为 NULL，如何 select 下一个值

Question

I am trying to write those Select subquery so that if the Top 1 value is NULL, it would move to the next value that is not NULL. Here is the code:

----------------- GATHERING DATE DATA FROM ALL 12 MONTH UDF'S INTO TEMP TABLE #tmpAll12MonthForms -----------------
select e.RECORD_ID,e.FORM_INSTANCE_ID,e.FORM_NAME,e.[FIELD_VALUE] as [DATE_FORM_COMPLETED],
    row_number() over (partition by record_id order by cast([FIELD_VALUE] as date) desc) as RowNum into #tmpAll12MonthForms
    from [View_CMMode_UDFData] e
    where e.FORM_DEF_DR IN 
    ('HMFPAT12mPostEn','HMFPAT24mPostEn','HMFPAT36mPostEn'
    ,'HMFPAT48mPostEn','HMFPAT60mPostEn'
    ,'HMFPAT72mPostEn','HMFPATEnroll','PATEnroll'
    ,'HMFPATEnrollV01','SCMTmechvEnroll','HMFSCEnroll','HMFNFP12mPostEn'
    ,'HMFNFP24mPostEn','HMFNFPEnroll')
    AND e.FIELD_DEF_DR in ('PATMIECHV12mPostEn','PATMIECHV24mPostEn'
    ,'PATMIECHV12mPostEnGuideDtVstFrmComp'
    ,'PATMIECHV24mPostEnGuideDtVstFrmComp'
    ,'PATMIECHV36mPostEnGuideDtVstFrmComp'
    ,'MTmechv48mPostEnGuideDt','MTmechv60mPostEnGuideDt'
    ,'MTmechv72mPostEnGuideDt' ,'PATEnrollGuideDt','EnrollGuideDt'
    ,'FSMTmechv12mPostEn','FSMTmechv12mPostEnGuideDt'
    ,'NFPMIECHV12mUpdtGuideDt','NFPMIECHV18mUpdtGuideDt'
    ,'NFPMIECHV24mUpdtGuideDt','NFPMIECHV6mUpdtGuideDt'
    ,'NFPMIECHVEnrollGuideDt')
    group by e.record_id,e.FORM_INSTANCE_ID,FORM_NAME,[FIELD_VALUE]

create unique clustered index All12MonthFormsU on #tmpAll12MonthForms (record_id,form_instance_id)

----------------- GATHERING PRENATAL ENROLLIES DATA FROM UDF INTO TEMP TABLE #tmpPrenatal -----------------
SELECT [RECORD_ID],[FORM_INSTANCE_ID],[field_value] as 'Prenatal status' INTO #tmpPrenatal
    FROM [View_CMMode_UDFData]
    where [SECTION_DEF_DR] in ('MTmechvEnrollInfo','FP') and [FIELD_DEF_DR] in ('MTmechvEnrollInfoChldPNEnroll','FPPG')
    GROUP BY [RECORD_ID],[FORM_INSTANCE_ID],[field_value]

------------- COLLECTING CLIENT PRENATAL ENROLLMENT DATA FOR PAT --------------------
SELECT U.RECORD_ID,u.FORM_INSTANCE_ID,u.[Prenatal status],p.RowNum into #TmpPrenatalEnrollPAT
    FROM #tmpPrenatal u inner join #tmpAll12MonthForms p 
    on p.RECORD_ID = u.RECORD_ID and p.FORM_INSTANCE_ID = u.FORM_INSTANCE_ID 
    group by U.RECORD_ID,u.FORM_INSTANCE_ID,u.[Prenatal status],p.RowNum

----------- THIS IS THE SELECT SUBQUERY I AM WORKING ON. THERE ARE MANY LIKE THIS ONE -------------
,(SELECT TOP 1 [Prenatal status]
FROM #TmpPrenatalEnrollPAT as prenatalEnroll WHERE prenatalEnroll.RECORD_ID = ClientSVC.SVC_ID
ORDER BY prenatalEnroll.RowNum asc
) AS PrenatalEnroll
 ............
 ............

 INTO #TempPrimaryCGPAT
 FROM #tmpClientServices AS ClientSVC 
 INNER JOIN #tmpClients AS Client ON Client.PER_ROWID = ClientSVC.SVC_PersonDR

 SELECT .....................
      ,ClientSVC.PER_PRIMARYLANGUAGE as Client_PrimaryLanguage
      ,PrenatalEnroll as [Prenatally Enroll]
      ,ClientSVC.EnrollDate
      ,.............
  into #TMPpatTable
  FROM #TempPrimaryCGPAT AS ClientSVC
  INNER JOIN E_Entity e (nolock) ON e.ID = ClientSVC.PrimaryCGID
  INNER JOIN #tmpClients AS CAREGIVER ON CAREGIVER.PER_ROWID = e.EntityHx_ID
  INNER JOIN #tmpLastHomeVisitPAT V ON V.RECORD_ID = ClientSVC.SVC_ID

I would need the code to move on to the next value from the Top 1. RowNum in the Order clause is a row number that was created using a partition in a previous table and as things stand it is equal to 1. This is one of many Select subqueries using this Select Top 1 method. I am using this method to get the most recent information from the query, but if needed, we could fall back on the next most recent data.

Here is some sample output. The entire output is very large with many columns.

  Caregiver_MaritalStatus
          Married
  Not Married but Living Together with Partner
           NULL
  Not Married but Living Together with Partner
  Never Married (not including not married but living with partner)
  Not Married but Living Together with Partner
           NULL
         Married
  Not Married but Living Together with Partner
  Not Married but Living Together with Partner
  Not Married but Living Together with Partner

Answer 1

To explain what I think this could be, take this simple query

SELECT 
    (SELECT TOP 1 t.name from sys.tables T 
                WHERE 1 = 0 
                AND t.name IS NOT NULL 
                order by T.name
    ) DQ

t.name is probably never NULL, and I would never select it, but I never select a row in any case, so you do see NULL - the subquery returns nothing, NULL

this second query shows that there are 0 rows, not that NULL field is being obtained by the query

    SELECT 
    (SELECT  COUNT(t.name) from sys.tables T 
                WHERE 1 = 0 
                AND t.name IS NOT NULL 

    ) DQ

Answer 2

inner join (SELECT [Prenatal status], RECORD_ID, RowNum
            FROM #TmpPrenatalEnrollPAT
            WHERE RowNum < 4
           ) PreNatalEnroll on PreNatalEnroll.RECORD_ID = ClientSVC.SVC_ID