t-sql 2012 prefer to not use union all

• dianerstein 8713

  SSCrazy

  Points: 2197

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  January 26, 2017 at 1:13 pm

  #339733

  

  0

  In t-sql 2012, the following sql works when I use a union all statement. However I would prefer not to
  use a union all if at all possible. The problem is there are  a few times when the join does not find anythning.
  When the join occurs there are some cases where attributeID= 997 or 1452, does not have a match by personID.
  The goal is is there is value <>'N' in all cases, the result attributeID value should be set to 3370.
   Select c1.personID
            ,c1.enrollmentID
            ,attributeID=case when c2.value = 'N' then 3371 else 3370 end
            ,c1.value
      ,c1.date
      ,c1.customGUID
      ,c1.districtID
      ,c2.value
    from O.dbo.CustC1
    JOIN   O.dbo.Custc2
       on  c2.personID=c1.personID
        and c2.date = c1.date
     and C2.attributeID= 997
    where  C1.attributeID = 1452
    UNION ALL
    Select c3.personID
            ,c3.enrollmentID
            ,attributeID=3370
      ,c3.value
      ,c3.date
      ,c3.customGUID
      ,c3.districtID
      ,value=''
   from O.dbo.CustC3
      where  C3.attributeID = 1452
       and c3.personID not in
    (select c4.personID from O.dbo.CustC4
       where c4.attributeID= 997)

  Thus can you modify the sql above to meet my requirement?

• Luis Cazares

  SSC Guru

  Points: 183686

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  January 26, 2017 at 1:26 pm

  #1925190

  I'm assuming that it's only one table with 4 different alias. It could be handled by a left join.
  
Select c1.personID
  ,c1.enrollmentID
  ,attributeID=case when c2.value = 'N' then 3371 else 3370 end
  ,c1.value
  ,c1.date
  ,c1.customGUID
  ,c1.districtID
  ,ISNULL( c2.value, '') AS value
from O.dbo.Cust C1
LEFT
JOIN O.dbo.Cust C2 on c2.personID=c1.personID
      and c2.date = c1.date
      and C2.attributeID= 997
where C1.attributeID = 1452


  Luis C.
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