join 2 tables without duplicate rows

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join 2 tables without duplicate rows

mattech06

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Points: 2484
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January 2, 2014 at 2:04 am

#284084

Having a bit of a brain freeze at the moment!
I wish to extract data from 2 tables which are linked by dbPatID but don't want duplicate rows created when there is more than one occurrence of dbPatID in table 2 which is what this sql is bringing back.
Select EPSAgedBalances.dbPatID, EPSAgedBalances.dbPatFirstName, EPSAgedBalances.dbPatLastName,
EPSAllContracts.dbStaffLastName, EPSAgedBalances.TotTot
from EPSAgedBalances
inner join EPSAllContracts on EPSAllContracts.dbPatID = EPSAgedBalances.dbPatID
where EPSAgedBalances.TotTot < 0
In other words I'm just after the dbStaffLastName from table 2 that matches up with dbPatID.
thanks

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Abu Dina SSChampion Points: 14155 More actions · Answer 1

Happy new year! 😀

So one contract can have multiple aged balances?

How about the below:

Select b.dbPatID, a.dbPatFirstName, a.dbPatLastName, b.dbStaffLastName, SUM(a.TotTot) AS TotTot

from EPSAgedBalances AS a

inner join EPSAllContracts AS b

on b.dbPatID = a.dbPatID

GROUP BY b.dbPatID, a.dbPatFirstName, a.dbPatLastName, b.dbStaffLastName

HAVING SUM(a.TotTot) < 0

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ChrisM@Work SSC Guru Points: 186127 More actions · Answer 2

Here's an alternative to Abu Dinas' suggestion;

SELECT

b.dbPatID,

b.dbPatFirstName,

b.dbPatLastName,

x.dbStaffLastName,

b.TotTot

FROM EPSAgedBalances b

CROSS APPLY (

SELECT TOP 1 dbStaffLastName

FROM EPSAllContracts c

WHERE c.dbPatID = b.dbPatID

) x

WHERE b.TotTot < 0

Not necessarily better - you should try both and compare performance.

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

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mattech06 SSCrazy Points: 2484 More actions · Answer 3

Hi Guys, thanks for your help. I found simply adding distinct has done the trick

Select distinct EPSAgedBalances.dbPatID, EPSAgedBalances.dbPatFirstName, EPSAgedBalances.dbPatLastName,
EPSAllContracts.dbStaffLastName, EPSAgedBalances.TotTot
from EPSAgedBalances, EPSAllContracts
where EPSAllContracts.dbPatID = EPSAgedBalances.dbPatID
and TotTot < 0

thanks