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aggregate function

aggregate function

aggregate function

(OP)
The query (B) below is working, but in the first LEFT JOIN I'd like to pull the most recent result.  So, I'd have to add something like the query (A) below in somehow.

A
SELECT poArID, poDatetime FROM posts ORDER BY poDatetime DESC

B
SELECT articles.arID, articles.arType, articles.arTitle, articles.arDescr, articles.arCl, articles.arURL, posts.poTxt, posts.poDatetime, posts.poAd, posts.poArID, advisors.adLname, advisors.adID, advisors.adFname, advisors.adTitle  
FROM articles
LEFT JOIN posts ON articles.arID = posts.poArID
LEFT JOIN advisors ON posts.poAd = advisors.adID
WHERE arCl = '" . $clID . "'
GROUP BY articles.arTitle
ORDER BY articles.arTitle ASC ";

RE: aggregate function

CODE

SELECT articles.arID
     , articles.arType
     , articles.arTitle
     , articles.arDescr
     , articles.arCl
     , articles.arURL
     , posts.poTxt
     , posts.poDatetime
     , posts.poAd
     , posts.poArID
     , advisors.adLname
     , advisors.adID
     , advisors.adFname
     , advisors.adTitle
  FROM articles
LEFT OUTER
  JOIN ( SELECT poArID
              , MAX(poDatetime) AS latest
           FROM posts
         GROUP
             BY poArID ) AS m
    ON m.poArID = articles.arID

LEFT OUTER
  JOIN posts
    ON posts.poArID = articles.arID
   AND posts.poDatetime = m.latest
LEFT OUTER
  JOIN advisors
    ON advisors.adID = posts.poAd
 WHERE articles.arCl = ". $clID ." -- no single quotes
GROUP
    BY articles.arTitle
ORDER
    BY articles.arTitle ASC
 

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