mysql MAX查询未在加入时返回最新记录
我有一个查询返回了正确的数据,除了左连接没有返回最新的记录(按日期上传列排序),谢谢您的帮助mysql MAX查询未在加入时返回最新记录,mysql,sql,Mysql,Sql,我有一个查询返回了正确的数据,除了左连接没有返回最新的记录(按日期上传列排序),谢谢您的帮助 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 =
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
您需要一个预查询来获取每个相册上载的最大日期,然后可以根据匹配的相册和日期限定符获取正确的相册条目
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 ?,?;
MAX
不应返回最新记录。它只应返回单个列(或表达式)的最大值。您知道如何更改查询以获取最新的照片记录通用解决方案是这样的:更好的通用解决方案是使用自连接而不是子查询: