参考的实体与功能NHibernate公式 [英] Reference an entity with a formula in Fluent NHibernate

问题描述

我用 N A模式：存储在另一个表，是由一个公式选择1 亲子关系。是否有可能映射该实体使用公式父？

 公共类ParentEntity {
公共虚拟INT的ParentId {搞定;组; } 
公共虚拟ChildEntity儿童{搞定;组; } 
} 
 
 
公共类ParentMapping：ClassMap< ParentEntity> {
公共ParentMapping（）{
表（ParentTable）; 
 
标识（X => x.ParentId）。.Column（的ParentId）GeneratedBy.Assigned（）Not.Nullable（）; 
参考< ChildEntity>（X => x.Child）.Formula（
 @（
选择TOP 1 ChildTable.ChildId 
 FROM ChildTable 
，其中ChildTable。的ParentId =的ParentId 
）
）; 
} 
} 
  

这是该映射产生这样看起来SQL：

  SELECT 
 this_.ParentId，
 this_.ChildEntity_id 
 FROM ParentTable THIS_ 
  

这是不是我要找的。

我怎样才能在父表中引用该子实体和使用，而不是 childID的，从选择 childID的公式公式？

解决方案

的我不会无论如何讨论这种方法的正确性，只是尽量回答。什么你正在尝试做的：应的工作。我检查了公式的正确性测试场景。所以，是的公式可以准确地使用这种方法。

但因为它不工作，我会有点猜测。让我们开始在我的测试情况下，这是工作生成的SQL。

  SELECT this_.ParentId作为ParentId3_0_ 
，（ SELECT TOP 1 Child.ChildId 
从小孩
其中Child.ParentId = this_.ParentId）作为formula1_0_ 
从父THIS_ 
  

可能出现的问题

我看到了两个可能的问题。

1。

  
 
 
都在你的代码段的第一>引用< ChildEntity>（X => x.Child）.Formula（
 @（
选择TOP 1 ChildTable.ChildId 
 FROM ChildTable 
其中ChildTable.ParentId =的ParentId 
）
  

是子主键的列名： childID的 而在SQL片段是在 ChildEntity_id

  SELECT 
 this_.ParentId，
 this_.ChildEntity_id 
 FROM ParentTable THIS_ 
  

2。SQL片段不匹配

其次，你提到的（SQL语句只是以上）是生成什么，但它更像是这个映射的语句：

 引用< ChildEntity>（X => ; x.Child）.Column（ChildEntity_id）
  

所以，不可能是有一些较旧的/其他映射，这实际上是在用吗？

摘要
我想说的话，该映射的这种方式工作。那么，你是正确的轨道上，但是的魔鬼隐藏在细节的;）

I have a schema with an N:1 parent-child relationship that is stored in another table and is selected by a formula. Is it possible to map this entity to the parent using a formula?

public class ParentEntity {
    public virtual int ParentId { get; set; }
    public virtual ChildEntity Child{ get; set; }
}


public class ParentMapping : ClassMap<ParentEntity> {
    public ParentMapping() {
        Table("ParentTable");

        Id(x => x.ParentId).Column("ParentId").GeneratedBy.Assigned().Not.Nullable();
        References<ChildEntity>(x => x.Child).Formula(
            @"(
                SELECT TOP 1 ChildTable.ChildId
                FROM ChildTable
                WHERE ChildTable.ParentId = ParentId
            )"
        );
    }
}

The SQL that this mapping generates looks like this:

SELECT
    this_.ParentId,
    this_.ChildEntity_id
FROM ParentTable this_ 

This is not what I'm looking for.

How can I reference this child entity and use, instead of ChildId in the parent table, a formula that selects ChildId from a formula?

解决方案

I won't anyhow discuss the correctness of this approach, just try to answer. What you are trying to do: should work. I've checked the correctness of the formula in a test scenario. So, yes formula could be used exactly this way.

But because it is not working, I would a bit guess. Let's start with SQL generated in my test case, which is working.

SELECT this_.ParentId as ParentId3_0_
, (SELECT TOP 1 Child.ChildId
     FROM Child
     WHERE Child.ParentId = this_.ParentId) as formula1_0_ 
FROM Parent this_

Possible issues

I see two possible issues

1. Different Child ID column names

First of all in your snippet:

References<ChildEntity>(x => x.Child).Formula(
            @"(
                SELECT TOP 1 ChildTable.ChildId
                FROM ChildTable
                WHERE ChildTable.ParentId = ParentId
            )"

is column name of child primary key: ChildId while in SQL snippet is the ChildEntity_id:

SELECT
    this_.ParentId,
    this_.ChildEntity_id
FROM ParentTable this_ 

2. SQL Snippet does not match

Secondly, you mentioned that the (SQL Statement just above) is what was generated. But it is more like a statement of this mapping:

References<ChildEntity>(x => x.Child).Column("ChildEntity_id")

So couldn't be there some older/other mapping, which is in fact used?

SUMMARY I wanted to say, that this way of mapping is working. So you are on the correct track, but the devil is hidden in details ;)

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