如何将带有联合的SQL查询转换为LINQ? [英] How to convert SQL query with Unions to LINQ?
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问题描述
如何将其转换为LINQ?
How to convert this one to LINQ?
select d.UserID, d.Content, d.UpdateTime
from DiaryPosts as d
where d.UserID = 1
/* Friends posts */
Union
select d.UserID, d.Content, d.UpdateTime
from DiaryPosts as d
join Friends as fr
on d.UserID = fr.FriendID
where fr.UserID = 1
/* My followings */
Union
select d.UserID, d.Content, d.UpdateTime
from DiaryPosts as d
join Followers as fl
on d.UserID = fl.FollowerID
where fl.UserID = 1
/* order by UpdateTime desc */
order by 3 desc
我尝试过:
var diaryPosts = (from d in db.DiaryPosts
join e in db.EstadosDeAlma
on d.EstadosDeAlmaID equals e.ID
join u in db.User
on d.UserID equals u.ID
join fr in db.Friends
on d.UserID equals fr.FriendID
where fr.UserID == userset.ID
join fl in db.Followers
on d.UserID equals fl.UserID
where fl.FollowerID == userset.ID
orderby d.ID descending
select new DiaryPostsSet
{
PostID = d.ID,
EstadoDeAlmaID = e.ID,
EstadoDeAlma = e.Title,
Author = u.Nickname,
Thumbnail = u.Thumbnail,
AuthorComment = d.Content,
UserID = u.ID,
IsDuplicated = d.IsDuplicated,
FriendID = d.FriendID,
FriendName = u.Nickname,
Time = d.UpdateTime,
MessagesCount = d.FriendMessages.Count(m => m.DiaryPostsID == d.ID)
}).Take(6).ToList();
它没有显示任何结果.我尝试使用EF子句,但是当我拥有Union时,我不知道如何执行下一个Join.
It doesn't show me any result. I tried with EF clauses but when I have Union, I don't know how to perform the next Join.
有人可以帮我吗?
推荐答案
有一个联合方法
这是一个提示.当事情变得困难时,将其分解,然后简化.我将帮助您解决问题,并将简化过程留给您.
Here is a hint. When things get difficult break them down, then simplify. I will help you break down the problem and leave the simplification to you.
var query1 = (from d in db.DiaryPosts
where d.UserID = 1
select new {
UserID = d.UserID
Content = d.Content
UpdateTime = d.UpdateTime
}).ToList();
var query2 = (from d in db.DiaryPosts
join f in db.Friends
on d.UserId = f.FriendId
where f.UserId = 1
select new {
UserID = d.UserID
Content = d.Content
UpdateTime = d.UpdateTime
}).ToList();
var query3 = (from d in db.DiaryPosts
join f in db.Followers
on d.UserId = f.FollowerID
where f.UserId = 1
select new {
UserID = d.UserID
Content = d.Content
UpdateTime = d.UpdateTime
}).ToList();
var myunionQuery = query1.Union(query2).Union(query3).OrderBy(d => d.UpdateTime);
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