Book Image

NHibernate 2 Beginner's Guide

By : Aaron Cure
Book Image

NHibernate 2 Beginner's Guide

By: Aaron Cure

Overview of this book

<p>NHibernate is an open source object-relational mapper, or simply put, a way to retrieve data from your database into standard .NET objects. Quite often we spend hours designing the database, only to go back and re-design a mechanism to access that data and then optimize that mechanism. This book will save you time on your project, providing all the information along with concrete examples about the use and optimization of NHibernate.<br /><br />This book is an approachable, detailed introduction to the NHibernate object-relational mapper and how to integrate it with your .NET projects. If you're tired of writing stored procedures or maintaining inline SQL, this is the book for you.<br /><br />Connecting to a database to retrieve data is a major part of nearly every project, from websites to desktop applications to distributed applications. Using the techniques presented in this book, you can access data in your own database with little or no code.<br /><br />This book covers the use of NHibernate from a first glance at retrieving data and developing access layers to more advanced topics such as optimization and Security and Membership providers. It will show you how to connect to multiple databases and speed up your web applications using strong caching tools. We also discuss the use of third-party tools for code generation and other tricks to make your development smoother, quicker, and more effective.</p>
Table of Contents (19 chapters)
NHibernate 2
Credits
About the Author
About the Reviewers
Preface
Index

Relationships


Remember all those great relationships we created in our database to relate our tables together? If you need a refresher, then head back over to the Relationships section of Chapter 2, Database Layout and Design. Basically, the primary types of relationships are as follows:

  • One-to-many (OTM)

  • Many-to-one (MTO)

  • One-to-one (OTO)

  • Many-to-many (MTM)

We won't focus on the OTO relationship because it is really uncommon. In most situations, if there is a need for a one-to-one relationship, it should probably be consolidated into the main table.

One-to-many relationships

The most common type of relationship we will map is a one-to-many (OTM) and the other way—many-to-one (MTO). If you remember, these are just two different sides of the same relationship, as seen in the following screenshot:

This is a simple one-to-many (OTM) relationship where a Contact can be associated with zero to many OrderHeader records (because the relationship fields allow nulls). Notice that the Foreign Key for...