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Question

I keep getting duplicates on my join statement , any join experts please help I have been scratching my head for hours

SELECT  
  DISTINCT  
  image.ImageID,
  Lotpw.Lot,
  lot.Oper,
  lot.Product,
  lot.Process,
  Image.PartialWafer,
  image.UnitX,
  image.UnitY,
  Image.InspectionStation,
  Image.Status,
  Image.ImagePath,
  image.Date,
FROM Lot 
--FROM [VueDb].[dbo].[Lot] join [VueDb].[dbo].[LotPW] on lot.Lot=lotpw.Lot join [VueDb].[dbo].[Image] on lotpw.PartialWafer = image.PartialWafer 
  LEFT JOIN LotPW 
    on lot.Lot = lotpw.Lot  
  RIGHT JOIN image 
    on LOTPW.partialwafer = Image.partialwafer

WHERE (@Lot= '' or  Lot.Lot= @Lot)
  and (@Oper ='' or Lot.Oper= @Oper)
  and (@Product= '' or  Lot.Product= @Product)
  and (@Process= '' or Lot.Process= @Process)
  and (@PartialWafer= '' or  image.PartialWafer= @PartialWafer)
  and (@UnitX ='' or Image.UnitX= @UnitX)
  and (@UnitY= '' or Image.UnitY= @UnitY)
  and (@InspectionStation ='' or Image.InspectionStation = @InspectionStation)
  and (@Status ='' or Image.Status= @Status)
  and (@LossCode= '' or Image.LossCode= @LossCode)

below is an image of the output

Answer 1

(Not a solution but might help)

Try this like Philip suggests and then inspect the data:

SELECT  
  *
FROM Lot 
  LEFT JOIN LotPW 
    on lot.Lot = lotpw.Lot  
  RIGHT JOIN image 
    on LOTPW.partialwafer = Image.partialwafer

I'm guessing you need to add other conditions into your ON clauses.

Answer 2

From the way your query is setup, it looks like Lot is the top of the hierarchy, and has a 1:n relationship with LotPW (LotPW.Lot is suggesting the column:Lot is the PK on table:Lot, and thus the column:Lot is a FK on LotPW). The left join suggest that you don't think each Lot row has a LotPW row (child) in the database. This join will produce multiple rows any time there is more than 1 row in Lot which matches with LowPW.

The join to Image suggests that LotPW is the parent in this relationship, and that LotPW.PartialWafer is the PK on the LotPW table. With this join being a Right Join to LotPW, it's saying that you don't believe that each PW has a parent. This right Join should probably be a left join, otherwise you're negating the Left Join between Lot and LotPW

To de-dupe this, assuming multiple rows may be present in Lot or LotPW which match to a given PW, but you don't care about the extra data, do the join between Lot and LotPW and Group By on all values. Then use this resultset in the Left/Right Join with PW.

something like:

     Select distinct
        image.ImageID,
        Lotpw.Lot,
        lot.Oper,
        lot.Product,
        lot.Process,
        Image.PartialWafer,
        image.UnitX,
        image.UnitY,
        Image.InspectionStation,
        Image.Status,
        Image.ImagePath,
        image.Date
     From 
        (select Lot.Lot, Lot.Oper, lot.Product, lot.process, LotPW.PartialWafer 
            From Lot left join LotPW on Lot.Lot = LotPW.Lot
            Group by Lot.Lot, Lot.Oper, lot.Product, lot.process) UniqueLots
       Left Join Image on Image.PartialWafer = UniqueLots.PartialWafer

Answer 3

Every row in your list is distinct; select distinct is a row operator meaning it works across the entire row . Notice (in yellow) that every row does have something different. pxq100 != pxq200 and so on.

So, if you have used select distinct and you think you still think you are getting duplicates then you just haven't used the right technique because select distinct only does one thing , you need GROUP BY or ROW_NUMBER()