Selecet DISTINCT plus one more

Question

Selecet DISTINCT plus one more

flyadvertising (Programmer)

(OP)

6 Feb 11 01:27

The following is working great, but I need to get one more row from the second table (ppics). However, when I try to add this in, my query stops working. Any help will be much appreciated.

SELECT ppre.cID, ppre.yr, ppre.make, ppre.model, ppre.vin, ppre.display FROM ppre
JOIN (SELECT DISTINCT pcID FROM ppics) AS TR
ON TR.pcID = ppre.cID

r937 (TechnicalUser) · Answer 1 · 2011-02-06 02:19:02

which row did you want?

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flyadvertising (Programmer) · Answer 2 · 2011-02-06 02:23:15

RE: Selecet DISTINCT plus one more

flyadvertising (Programmer)

(OP)

6 Feb 11 02:23

I'd like to return ppics.purl

r937 (TechnicalUser) · Answer 3 · 2011-02-06 02:29:07

oh, you mean an extra column, not row

CODE

SELECT ppre.cID
     , ppre.yr
     , ppre.make
     , ppre.model
     , ppre.vin
     , ppre.display
     , TR.purl
  FROM ppre
INNER
  JOIN ( SELECT DISTINCT
                pcID
              , purl
           FROM ppics ) AS TR
    ON TR.pcID = ppre.cID

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flyadvertising (Programmer) · Answer 4 · 2011-02-06 02:38:39

Right, an extra column.

However, the SQL you provided shows all the results (not right). My original statement showed just the distinct TR.pcID's (right), but I am just trying to pull in the associated value from the ppics.purl in the same row as the TR.pcID. Sorry if I am not being clear.

flyadvertising (Programmer) · Answer 5 · 2011-02-06 02:42:33

This did it:

SELECT ppre.cID, ppre.yr, ppre.make, ppre.model, ppre.vin, ppre.display, TR.purl FROM ppre INNER JOIN ( SELECT DISTINCT pcID, purl FROM ppics ) AS TR ON TR.pcID = ppre.cID GROUP BY ppre.cID

Thank you

r937 (TechnicalUser) · Answer 6 · 2011-02-06 09:45:13

Quote:
but I am just trying to pull in the associated value from the ppics.purl

if there was only one purl for each pcID in ppics, then you wouldn't have to do the GROUP BY in the outer query

and since you do have to, that means that there are multiple purl values for each ppre.cID

which means when you GROUP BY BY ppre.cID in the outer query, without applying an aggregate function to purl, you get an indeterminate value for purl -- it could be any one of the values associated with that cID

this is explained here: GROUP BY and HAVING with Hidden Columns

does that help?

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r937 (TechnicalUser) · Answer 7 · 2011-02-06 09:50:39

and of course in ANSI SQL you are not allowed to omit columns from the GROUP BY clause like you can in mysql

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flyadvertising (Programmer) · Answer 8 · 2011-02-06 21:11:20

Yes, that helps, thanks. Fortunately, pulling any of the purl values associated with that cID satisfies what I need to do. However, I will look at the aggregate function so I can make the query more accurate.

Again, thanks for your help.

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Selecet DISTINCT plus one more