Question

LINQ查询

from rc in context.RC
join r in context.R on rc.RId equals r.Id 
join c in context.C on rc.CId equals c.Id 
join f in context.F on rc.FId equals f.Id into fg
from f in fg.DefaultIfEmpty()
join e in context.E on rc.EId equals e.Id into eg
from e in eg.DefaultIfEmpty()

生成的SQL

SELECT  *
FROM    [dbo].[RC] AS [Extent1]
        INNER JOIN [dbo].[R] AS [Extent2] ON [Extent1].[RId] = [Extent2].[Id]
        INNER JOIN [dbo].[C] AS [Extent3] ON [Extent1].[CId] = [Extent3].[Id]
        INNER JOIN [dbo].[F] AS [Extent4] ON [Extent1].[FId] = [Extent4].[Id]
        INNER JOIN [dbo].[E] AS [Extent5] ON [Extent1].[EId] = [Extent5].[Id]

我想要的是

SELECT  *
FROM    [dbo].[RC] AS [Extent1]
        INNER JOIN [dbo].[R] AS [Extent2] ON [Extent1].[RId] = [Extent2].[Id]
        INNER JOIN [dbo].[C] AS [Extent3] ON [Extent1].[CId] = [Extent3].[Id]
        LEFT JOIN [dbo].[F] AS [Extent4] ON [Extent1].[FId] = [Extent4].[Id]
        LEFT JOIN [dbo].[E] AS [Extent5] ON [Extent1].[EId] = [Extent5].[Id]

不确定我的LINQ查询中缺少什么

代码的屏幕截图

更新

基于@GertArnold的评论，RC-F（表格）和RC-E（表格）位于N-1关联中，其中RC应包含有效的ID密钥参考F，但在RC表格中，有些F ID为零，我在执行inner join时会跳过数据。

那么现在如何在不修改我的数据库架构的情况下强制Entity-Framework / LINQ生成LEFT JOIN语法

Answer 1

基于@GertArnold的评论，RC-F（表格）和RC-E（表格）处于N-1关联，其中RC应该为F保存有效的id键参考，但在RC表中，有些F ID是零，在我进行内连接时跳过数据。

这就是我最终查询结果的方式。

            List<MyType> myResults;
            using (Entities context = new Entities())
            {
                var results = (from rc in context.RC
                    join r in context.R on rc.RId equals r.Id
                    join c in context.C on rc.CId equals c.Id
                    select rc).ToList();

                myResults = results.Select(rc => new MyType
                {
                    Id = rc.Id,
                    Rule = new IdName
                    {
                        Id = rc.R.Id,
                        Name = rc.R.Name
                    },
                    Conjuction = new IdName
                    {
                        Id = rc.C.Id,
                        Name = rc.C.Conjuncation
                    },
                    Field = new IdName
                    {
                        Id = rc.F!= null ? rc.F.Id : 0,
                        Name = rc.F!= null ? rc.F.Name : null
                    },
                    Expression = new IdName
                    {
                        Id = rc.E!= null ? rc.E.Id : 0,
                        Name = rc.E!= null ? rc.E.Expression : null
                    },
                    DisplayOrder = rc.Order,
                    Value1 = rc.Value,
                    Value2 = rc.Value2
                }).ToList();
            }

C＃LINQ中的左外连接

1 个答案: