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From: Markus Jelsma <markus@buyways.nl>
Reply-To: markus@buyways.nl
Organization: Buyways
To: user@couchdb.apache.org
Subject: Re: Tips for many to many
Date: Thu, 11 Feb 2010 14:18:46 +0100
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Hi,


You can explicitely list the relations for each entity in its own document, 
negating the need for a link-table.

doc{
 _id : channel_x1
 type : channel
 ..
 ..
 lineups : [lineup_y1, lineup_y2]
}

Now you have a channel document pointing to 0-n lineups. Obviously, for 
lineups you'll do it the other way around!

doc{
 _id : lineup_y1
 type : lineup
 ..
 ..
 lineups : [channel_x1, channel_x2]
}

An other possibility is embedding all related data in a master document, but 
that may be hard to handle depending on your use case.


Cheers,


>If I have a true many to many relationship that doesn't normalize easily,
>what are some guidelines to make it couch-friendly?
>
>I've found that couch does a great job with one-to-many or one-to-one
>relationship. It's easy to write a view that will return all the comments
>for a given post, for example.
>
>But what about many-to-many? For example, I'm working with TV Guide data.
>There are lineups and channels. A lineup can have a lot of channels, but the
>channels can belong to several lineups. I then need to get what is playing
>at 2:00 on every channel in my lineup.
>
>Thanks

Markus Jelsma - Technisch Architect - Buyways BV
http://www.linkedin.com/in/markus17
050-8536620 / 06-50258350