Writing and Querying MapReduce Views in CouchDB

Relationships

While CouchDB has no built-in concept of relationships between documents, there are some techniques you can use to model relationships in your documents and views. The CouchDB Wiki page on Modeling Entity Relationships in CouchDB and Google’s Modeling Entity Relationships article were used as a reference for this section. If you’d like to compare the following examples to a relational database, please reference the column descriptions for the publisher (Table 5-1), book (Table 5-2), author (Table 5-3), and book_author (Table 5-4).

Table 5-1. Column descriptions from the publisher table

Field	Type	Null	Key	Default	Extra
publisher_id	varchar(255)	NO	PRI	NULL
name	varchar(255)	YES	NULL

Table 5-2. Column descriptions from the book table

Field	Type	Null	Key	Default	Extra
book_id	varchar(255)	NO	PRI	NULL
publisher_id	varchar(255)	YES	MUL	NULL
title	varchar(255)	YES	NULL
subtitle	varchar(255)	YES	NULL
formats	set('Print','Ebook','Safari Books Online')	YES	NULL
released	date	YES	NULL
pages	int(10) unsigned	YES	NULL

Table 5-3. Column descriptions from the author table

Field	Type	Null	Key	Default	Extra
author_id	varchar(255)	NO	PRI	NULL
firstname	varchar(255)	YES	NULL
lastname	varchar(255)	YES	NULL

Table 5-4. Column descriptions from the book_author junction table

Field	Type	Null	Key	Default	Extra
book_id	varchar(255)	NO	PRI	NULL
author_id	varchar(255)	NO	PRI	NULL

Warning

The relational database design outlined here is intended to make it easy for you to translate between the equivalent SQL and CouchDB queries. This is not necessarily a recommended database design. ...