这个 EF Join 方法调用有什么问题？

发布于 2024-10-10 04:16:39 字数 1031 浏览 1 评论 0原文

我目前仅限于在 EF4 数据存储库上使用扩展方法；我无法使用 linq to EF。我正在尝试使一个简单的 3 表连接工作。这是代码：

var query = _readOnlyRepository.All<Parent>()
            .Where( p => p.Something == "something" )
            .Join( _readOnlyRepository.All<Child>(), // Child entity
                p => p.ParentID,                     // Parent Key
                c => c.ChildId,                      // Child Key
                ( p, c ) => c )                      // Projection
            .Join( _readOnlyRepository.All<GrandChild>(),
                c => m.ChildID,
                g => g.GrandChildID,
                ( c, g ) => g )
            .Select( joined => joined.Child.Whatever );

这是（本质上）生成的 SQL：

select c2.Whatever
from Parent p
inner join Child c on p.ParentId = c.ParentId
inner join GrandChild g on c.ChildId = g.ChildId
left outer join Child c2 on g.ChildId = c2.ChildId
where ( "something" = p.Something )

我可以在代码中更改什么来消除使查询意图无效的左外连接？

原文

I'm currently restricted to using extension methods on an EF4 data repository; I can't use linq to EF. I'm trying to make a simple 3 table join work. Here is the code:

var query = _readOnlyRepository.All<Parent>()
            .Where( p => p.Something == "something" )
            .Join( _readOnlyRepository.All<Child>(), // Child entity
                p => p.ParentID,                     // Parent Key
                c => c.ChildId,                      // Child Key
                ( p, c ) => c )                      // Projection
            .Join( _readOnlyRepository.All<GrandChild>(),
                c => m.ChildID,
                g => g.GrandChildID,
                ( c, g ) => g )
            .Select( joined => joined.Child.Whatever );

Here is (essentially) the generated SQL:

select c2.Whatever
from Parent p
inner join Child c on p.ParentId = c.ParentId
inner join GrandChild g on c.ChildId = g.ChildId
left outer join Child c2 on g.ChildId = c2.ChildId
where ( "something" = p.Something )

What can I change in code to eliminate that left outer join that invalidates the intent of the query?

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那一片橙海， 2024-10-17 04:16:39

我不清楚你到底想返回什么——孙子的任何财产？您的第二个连接返回 GrandChild 对象 ( c, g ) => g 所以我认为你只需要

.Select( joined => joined.Whatever );

因为这里 joined 是 GrandChild 对象。

I'm not clear exactly what you're attempting to return - the Whatever property of the GrandChild? Your second join returns the GrandChild object ( c, g ) => g so I think you'd just need