MySQL: List rows who have one but not another many-to-many relationship

Posted by Svish on Stack Overflow See other posts from Stack Overflow or by Svish
Published on 2011-01-04T20:51:54Z Indexed on 2011/01/04 20:53 UTC
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mysql

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mysql-query

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join

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many-to-many

Not quite sure how to ask or define this, but can't figure it out.

I have three tables like this:

persons             person_id, first_name, last_name
hobbies             hobby_id, name
persons_hobbies     person_id, hobby_id

I need to make two lists. Persons that have both hobby A and B, and persons that have hobby A but not B. How can I write these two queries? Can't figure out how to do this with joining and all...

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