EF LINQ译:复杂查询 [英] EF LINQ translation: complex query
问题描述
我有这样的代码(注 l.FirstOrDefault()名称):
I have this code (Note l.FirstOrDefault().Name):
var qry = from peron in db.Persons
join room in db.Rooms on peron.Room.Id equals room.Id
join passport in db.Passports on peron.Passport.Id equals passport.Id
select new {peron.Fio, room.Name, passport.Number, Count = 0};
qry = qry.GroupBy(l => new {l.Fio, l.Number})
.Select(l => new {
l.Key.Fio,
l.FirstOrDefault().Name,
l.Key.Number,
Count = l.Count()
});
这转化为这样的:
SELECT
1 AS [C1],
[Project4].[Fio] AS [Fio],
[Project4].[C1] AS [C2],
[Project4].[Number] AS [Number],
[Project4].[C2] AS [C3]
FROM ( SELECT
[Project3].[Fio] AS [Fio],
[Project3].[Number] AS [Number],
[Project3].[C1] AS [C1],
(SELECT
COUNT(1) AS [A1]
FROM [dbo].[People] AS [Extent6]
INNER JOIN [dbo].[Passports] AS [Extent7] ON [Extent6].[Passport_Id] = [Extent7].[Id]
WHERE ([Extent6].[Room_Id] IS NOT NULL) AND (([Project3].[Fio] = [Extent6].[Fio]) OR (([Project3].[Fio] IS NULL) AND ([Extent6].[Fio] IS NULL))) AND (([Project3].[Number] = [Extent7].[Number]) OR (([Project3].[Number] IS NULL) AND ([Extent7].[Number] IS NULL)))) AS [C2]
FROM ( SELECT
[Distinct1].[Fio] AS [Fio],
[Distinct1].[Number] AS [Number],
(SELECT TOP (1)
[Extent4].[Name] AS [Name]
FROM [dbo].[People] AS [Extent3]
INNER JOIN [dbo].[Rooms] AS [Extent4] ON [Extent3].[Room_Id] = [Extent4].[Id]
INNER JOIN [dbo].[Passports] AS [Extent5] ON [Extent3].[Passport_Id] = [Extent5].[Id]
WHERE (([Distinct1].[Fio] = [Extent3].[Fio]) OR (([Distinct1].[Fio] IS NULL) AND ([Extent3].[Fio] IS NULL))) AND (([Distinct1].[Number] = [Extent5].[Number]) OR (([Distinct1].[Number] IS NULL) AND ([Extent5].[Number] IS NULL)))) AS [C1]
FROM ( SELECT DISTINCT
[Extent1].[Fio] AS [Fio],
[Extent2].[Number] AS [Number]
FROM [dbo].[People] AS [Extent1]
INNER JOIN [dbo].[Passports] AS [Extent2] ON [Extent1].[Passport_Id] = [Extent2].[Id]
WHERE [Extent1].[Room_Id] IS NOT NULL
) AS [Distinct1]
) AS [Project3]
) AS [Project4]
这是非常复杂的查询......但是如果我更换l.FirstOrDefault()的名字来命名=,我得到简单查询
It's very complex query... However if I replace l.FirstOrDefault().Name to Name = "", I get simple query
var qry = from peron in db.Persons
join room in db.Rooms on peron.Room.Id equals room.Id
join passport in db.Passports on peron.Passport.Id equals passport.Id
select new {peron.Fio, room.Name, passport.Number, Count = 0};
qry = qry.GroupBy(l => new {l.Fio, l.Number}).Select(l => new {l.Key.Fio, Name = "", l.Key.Number, Count = l.Count()});
SELECT
1 AS [C1],
[GroupBy1].[K1] AS [Fio],
N'' AS [C2],
[GroupBy1].[K2] AS [Number],
[GroupBy1].[A1] AS [C3]
FROM ( SELECT
[Extent1].[Fio] AS [K1],
[Extent2].[Number] AS [K2],
COUNT(1) AS [A1]
FROM [dbo].[People] AS [Extent1]
INNER JOIN [dbo].[Passports] AS [Extent2] ON [Extent1].[Passport_Id] = [Extent2].[Id]
WHERE [Extent1].[Room_Id] IS NOT NULL
GROUP BY [Extent1].[Fio], [Extent2].[Number]
) AS [GroupBy1]
我也得到简单的查询,如果我用这种方式
I also get simple query if I add room.Name to grouped fields and use by this way
var qry = from peron in db.Persons
join room in db.Rooms on peron.Room.Id equals room.Id
join passport in db.Passports on peron.Passport.Id equals passport.Id
select new {peron.Fio, room.Name, passport.Number, Count = 0};
qry = qry.GroupBy(l => new {l.Fio, l.Name, l.Number})
.Select(l => new
{
l.Key.Fio,
l.Key.Name,
l.Key.Number,
Count = l.Count()
});
我怎么可以解决这个问题的 l.FirstOrDefault()。名称 ?
感谢。
How I can fix the issue with l.FirstOrDefault().Name? Thanks.
推荐答案
既然你不订购组我以为你只是想任何名称从组。您可以使用像最高
比(是的,它的工作原理甚至字符串)的总和。我相信,这将产生一个比较合理的查询。
Since you are not ordering the group I assume you just want any of the names from the group. You can use an aggregate like Max
than (Yes it works even on strings). I believe that will generate a more reasonable query.
new {
l.Key.Fio,
Name = l.Max(x => x.Name),
l.Key.Number,
Count = l.Count()
});
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