如何使用 Nhibernate QueryOver 连接两个非 relashinship 定义的列的两个表 [英] How to join Two tables of two non relashinship defined columns using Nhibernate QueryOver

问题描述

使用 NHibernate QueryOver，我想使用在映射中未定义为关系的两列连接两个表.

Using NHibernate QueryOver, I want to join two tables using two columns which are not defined in the mapping as a relationship.

例如这不是我的确切场景，但这可以解释

E.g. This is not my exact scenario but this can explain that

表格:

Employee(Id, Name, DepartmentId, SomeCode,Address)

Department (Id, Name, ,Code)

选择

SELECT * 
  FROM EMPLOYEE E 
  JOIN DEPARTMENT D 
    ON D.Code = E.SomeCode

有人可以告诉我如何使用 NHibernate QueryOver 执行此查询.请注意，Employee 中的SomeCode"和Department 中的Code"并未定义为关系.DepartmentId 是外键，我可以使用 JoinAlias 加入这些外键，但我希望以不同的方式使用它.

Can someone please tell me how to do this query using NHibernate QueryOver. Note that "SomeCode" in Employee and "Code" in Department are not defined as a relationship. DepartmentId is the foreign key and I can join these using JoinAlias but I want it in a somewhat different way.

推荐答案

有类似的问题，例如

• NHibernate (+ FluentNhibernate):加入两个分离的表
• 没有映射表关联的休眠标准投影

答案是:

1. 使用 HQL 和 CROSS JOIN(带 WHERE)
2. 没有方法可以使用QueryOver/Criteria)

1. either use HQL and CROSS JOIN (with WHERE)
2. There is NO way how to do that with QueryOver/Criteria)

查看文档:

可能会出现多个类，导致笛卡尔积或交叉"连接.

Multiple classes may appear, resulting in a cartesian product or "cross" join.

from Formula, Parameter

from Formula as form, Parameter as param

因此在您的情况下使用 HQL，我们可以这样做:

So using HQL in your case, we can do it like this:

SELECT ...
FROM EMPLOYEE E, DEPARTMENT D 
WHERE D.Code = E.SomeCode
...

但我建议:在代码中创建该映射.简单介绍多对一关系.它将被延迟加载(仅在使用时)并且很好地满足我们的需求 - 在 QueryOver 中用作 Join

BUT I would suggest: create that mapping in the code. Simply introduce many-to-one relation. It will be loaded lazily (only if used) and will nicely serve to our needs - be used in QueryOver as a relation for Join

如果有这样的关系，如果这个存在于业务对象域中，我们不应该害怕使用它.我们可以通过安全等方式隐藏它...

If there is such relation, if this exist in the business object domain, we should not be scared to use it. We can hide it via security etc...

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