SQL Server MIN Funtion

Hi,

I have the SQL below. I am trying to get only one row with MiniMum Date (First Med Given Date and time). But it is returning multiple rows. Therefore, I am using Top 1 Function. Is there any other way to do this without Top Funtion? Please advise. Thanks

SELECT TOP 1
            DIS.EID,
            DIS.Institution,
            DIS.MRN,
            DIS.Account,
            DIS.AdmitDateTime,
            DIS.ERAdmitDtTm AS 'ED Received Date Time',
            Meds.[First Abx Admin Date],
            Meds.DrugName AS 'Antibiotic Name',
            (CASE      
                  WHEN (Meds.[First Abx Admin Date]) <= dateadd(hh,3, (CASE WHEN DIS.ERAdmitDtTm IS NULL THEN Dis.AdmitDateTime ELSE DIS.ERAdmitDtTm END))
                  THEN 'Y'
                  Else 'N'
            END) as ArrivalAbx
FROM      
            VISITPT_ALL_DIS AS DIS
            LEFT OUTER JOIN
                  (      SELECT
                              Med.EID,
                              Med.Account,
                              Med.DrugName,
                              MIN(MED.LastAdminDateTime)AS 'First Abx Admin Date'
                        FROM
                              MedAdminMAR_All_Adm AS MED
                        WHERE
                              Med.DrugID IN ( 'ACYC500I','AMIK500I','AMPH50I','AMPH50IL')
                        GROUP BY
                              Med.EID,
                              Med.Account,
                              Med.AdmitDateTime,
                              Med.DrugName
                        )Meds
            ON DIS.Account = Meds.Account
WHERE
      DIS.PatientType = 'IN'
      AND DIS.AccountStatus = 'DIS'  
ORDER BY
      DIS.Institution,
      DIS.MRN,
      DIS.Account,
      DIS.AdmitDateTime ,
      Meds.[First Abx Admin Date]
rustypootAsked:
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Anthony PerkinsConnect With a Mentor Commented:
Since you are getting multiple rows, they are probably coming from the JOIN'd table.  So you need to ask yourself
1. Why you are including Med.EID when you are not using it anywhere, either in the SELECT or JOIN.
2. Since you are selecting DrugName, which one do you want returned if there are multiple rows with a different DrugName?  The one with the oldest LastAdminDateTime?  If so what happens if there are two with the same LastAdminDateTime?
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Jim HornConnect With a Mentor Microsoft SQL Server Developer, Architect, and AuthorCommented:
The only Min() I see here is in a subquery, which is on the right side of a LEFT JOIN, which means all rows on the LEFT side (VISITPT_ALL_DIS AS DIS) will be returned in the result set.

So ... if you only want to return the one row, for starters change the LEFT JOIN to an INNER JOIN (or just JOIN).

Also, if DIS has a date that is the equivalent of MED.LastAdminDateTime, then you'll have to add that relationship to the JOIN clause, so the line below needs to change to the line below that:

             ON DIS.Account = Meds.Account

Open in new window

             ON DIS.Account = Meds.Account AND DIS.??Date = Meds.[First Abx Admin Date'] 

Open in new window

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AielloJCommented:
rustypoot

Without knowing more about your data model, it appears the root cause of the problem is a lack of the proper clauses in the WHERE clause.  I'm assuming 'Account' is the patient you are trying to get the one row for.

Since 'Account' is not in the WHERE clause, the first row for some random patient is probably being returned.

Best regards,

AielloJ
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awking00Commented:
select whatever from
(select whatever, row_number() over (partition by eid order by [first med given date and time] desc) rn
from yourtablejoin)
where rn = 1
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rustypootAuthor Commented:
Jim,

Thanks for the reply. But even if I change the JOIN to INNER JOIN, I get same # of rows. Also, there is no equivalent date to join on..
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awking00Commented:
Can you provide some relevant sample data (i.e. eliminate the extraneous fields and only include data meeting your filtering requirements other than the dates in question) and your expected output.
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