MySql中对Group by后的结果数进行Count

今天在写MySQ的SQL语句的时候遇到了一个奇怪的问题

1 select count(*) from subsitealbum t1, photo t2,files t3 
2           where t1.SourceAlbumId = t2.FolderId 
3           and t2.ID = t3.ID 
4           and t2.FolderId = t3.FolderID 
5           and SiteId in (select SubsiteID from channelsubsites where ChannelID='yszw') 
6     GROUP BY t1.Title,t1.Author, t3.Location,t2.CName,t2.LName,t3.Name

查询结果如下

改为以下语句后运行正常

select count(*) count from (select count(*) from subsitealbum t1, photo t2,files t3 
          where t1.SourceAlbumId = t2.FolderId 
             and t2.ID = t3.ID 
            and t2.FolderId = t3.FolderID 
           and SiteId in (select SubsiteID from channelsubsites where ChannelID='yszw') 
          GROUP BY t1.Title,t1.Author, t3.Location,t2.CName,t2.LName,t3.Name) temp

记得临时表一定要加别名，否则会报错