mysql MAX 查询在连接时不返回最新记录

Question

我有一个查询返回正确的数据，但左连接没有返回最新记录（按上传日期列排序） 感谢您的任何帮助。

select a.*,p.thumbnailphotopath as Picture from album_access ac 
inner join albums a on a.ID = ac.AlbumID 
left join (select albumid, thumbnailphotopath,max(DateUploaded) from photos where IsProcessed = 1 and IsPrivate = 0 GROUP BY albumID) p on a.ID = p.AlbumID #photos record not latest
where ac.AccessUserID = ? and ac.Ispending = 0 and ac.FullControl = 1 and a.Private = 1 order by a.DateCreated desc limit ?,?;
List of dates that return desc (its returning 2012-05-01 09:45:43 and thats not the latest)
2012-05-01 09:46:17 
2012-05-01 09:46:06
2012-05-01 09:45:43 --Returning this record 
2012-05-01 09:45:30
2012-05-01 09:39:49

Answer 1

您需要一个预查询来获取每个专辑上传的最大日期，然后可以根据匹配的专辑和日期限定符获取正确的专辑条目......

select 
      a.*,
      pFinal.thumbnailphotopath as Picture 
   from 
      album_access ac 
         inner join albums a
            on ac.AlbumID = a.ID
           AND a.Private = 1
         left join ( select
                           p.albumid,
                           max( p.dateUploaded ) as MaxDate
                        from
                           photos p
                        where
                               p.IsProcessed = 1
                           AND p.IsPrivate = 0
                        group by 
                           p.AlbumID ) pMax
            on ac.AlbumID = pMax.AlbumID 
               left join photos pFinal
                  on pMax.AlbumID = pFinal.AlbumID
                 AND pMax.MaxDate = pFinal.DateUpladed
   where 
          ac.AccessUserID = ? 
      and ac.Ispending = 0 
      and ac.FullControl = 1 
   order by 
      a.DateCreated desc 
   limit ?,?;