如何使用 NHibernate 调用从多个表返回结果的过程? [英] How to call a procedure using NHibernate that returns result from multiple tables?

问题描述

通常我们为每个表类创建 1:1 映射.

Normally we create 1:1 mapping per table-class.

Ex(表格):
[用户]
user_id - PK
姓名

[交易]
user_id - FK
item_id
金额

示例映射:
公共类用户
{
公共字符串 ID {get;设置;}
公共字符串名称{get;设置;}
}

公共类事务
{
公共字符串用户 ID {get;设置;}
公共字符串 ItemID {get;设置;}
公共十进制数量{get;设置;}
}

但出于优化考虑，有时在查询结果时需要进行操作；我们通常使用从多个表返回结果的存储过程.如果我们使用上面的例子；我们如何调用从连接表返回结果的过程?是否可以不创建一个新的类并仅仅为了这个组合记录而绑定?

Ex(Tables):
[users]
user_id - PK
name

[transactions]
user_id - FK
item_id
amount

Example mapping:
public class User
{
public string ID {get; set;}
public string Name {get; set;}
}

public class Transaction
{
public string UserID {get; set;}
public string ItemID {get; set;}
public Decimal Amount {get; set;}
}

But due to optimization concern and sometimes there are operations needed to be done while querying for results; we usually use stored procedures that returns result from multiple tables. If we use the example above; how can we call a procedure that returns results from the joined tables? Is it possible without creating a new class and binding just for the sake of this combined records?

谢谢！

推荐答案

在这种情况下可以使用存储过程，使用如下映射结构:

It is possible to use a stored procedure in this case, using a mapping construct like the following:

<sql-query name="LoadUsersAndTransactions" xml:space="preserve">
  <return class="User" alias="u">
    <return-property name="ID" column="user_id" />
    <return-property name="Name" column="name" />
  </return>
  <return-join property="u.Transactions" alias="t">
    <return-property name="key" column="user_id" />
    <return-property name="element" column="item_id" />
    <return-property name="element.id" column="item_id" />
    <return-property name="element.Amount" column="amount" />
  </return-join>
  EXEC dbo.SelectUsersAndTransactions :param_1, ..., :param_N
</sql-query>

这个例子假设 Transactions 被映射为 User 类上的一个包.您可以在 C# 中按如下方式使用此查询:

This example assumes that Transactions is mapped as a bag on the User class. You would use this query as follows from C#:

IList<User> users = session
    .GetNamedQuery("LoadUsersAndTransactions")
    .SetString("param_1", parameterValue1)
    ...
    .SetString("param_N", parameterValueN)
    .List<User>();

关于使用自定义 SQL 查询的 NHibernate 文档是 此处.

NHibernate documentation on usage of custom SQL queries is here.

干杯，格克.

这篇关于如何使用 NHibernate 调用从多个表返回结果的过程?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！