Question

我有一个查询，我知道它应该至少返回一行。如何修改我的跟随查询以确保相册返回数据。谢谢你的帮助。

在此查询。我知道专辑有一行，我需要退回它。

    select distinct p.*,
 a.ID as parentalbumid,a.CreatorID as albumcreatorid,a.AlbumName,a.AlbumDescription,a.AlbumDefaultImageURL,a.Private,a.DateCreated,a.AdultContent,a.PasswordProtected,a.AllowTags,a.TypeID,a.AlbumAutoID,
 mainuser.Username as mainuserusername,mainuser.ID as mainuserid,mainuser.PictureUrl as mainuserpictureurl,
c.ID as commentID,c.PhotoID as commentphotoid,c.OutputMessage,c.CommentDate,
t.ID as tagID,t.PhotoID as tagphotoid,t.UserID,t.TextTag,t.LeftLocation,t.TopLocation,
u.ID as userid,u.Username,u.FirstName,u.LastName,u.PictureUrl
from photos p
inner join albums a on a.ID = p.AlbumID
inner join users mainuser on mainuser.ID = p.UserID
left join comments c on c.PhotoID = p.ID
left join tags t on t.PhotoID = p.ID 
left join users u on u.ID = c.CommentBy
where a.AlbumAutoID = 3
order by p.DateUploaded desc;

Answer 1

仅使用LEFT JOIN（并将表格albums作为FROM的第一个表格）：

select distinct p.*,
 a.ID as parentalbumid,a.CreatorID as albumcreatorid,a.AlbumName,a.AlbumDescription,a.AlbumDefaultImageURL,a.Private,a.DateCreated,a.AdultContent,a.PasswordProtected,a.AllowTags,a.TypeID,a.AlbumAutoID,
 mainuser.Username as mainuserusername,mainuser.ID as mainuserid,mainuser.PictureUrl as mainuserpictureurl,
c.ID as commentID,c.PhotoID as commentphotoid,c.OutputMessage,c.CommentDate,
t.ID as tagID,t.PhotoID as tagphotoid,t.UserID,t.TextTag,t.LeftLocation,t.TopLocation,
u.ID as userid,u.Username,u.FirstName,u.LastName,u.PictureUrl
from albums a
left join photos p on a.ID = p.AlbumID
left join users mainuser on mainuser.ID = p.UserID
left join comments c on c.PhotoID = p.ID
left join tags t on t.PhotoID = p.ID 
left join users u on u.ID = c.CommentBy
where a.AlbumAutoID = 3
order by p.DateUploaded desc;

Mysql查询帮助。我需要确保至少有一条记录正在返回

1 个答案: