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    <p>I don't know what you mean by "belongs_to_many: through Books", but both habtm and hmt use a join table. If you have a many-to-many relationship there's no getting away from it. I don't understand how you plan to store multiple authors or topics on books table. If you combine the values in a single field you won't be able to join the authors or topics. If you have a fixed maximum you could add an association field for each one, but that seems kludgy in most cases.</p> <p>As for an example of primary data on a hmt relationship. Imagine that you were assuming that each topic had a specific chapter in a book (contrived I know, but it fits your model). The topic might be a different chapter in each book. In that case you would need to add the chapter field to the join table and use hmt.</p>
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    1. POHas and belongs to many vs. has many through
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    1. COYes, I meant "has many :through =>". Also, yes, both associations have a join table, but I am basically wondering if it's a smart idea to use a primary table (in this case the BOOKS table) to try to act as the join table for AUTHORS and TOPICS. Does that clarify? To answer your question, I would think the BOOKS table would contain author_id and topics_id, and so each book could refer to authors and topics that way. I'm just wondering if I'm overusing HMT by cluttering up my BOOKS table (using it as the join)?
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    2. COYou can definitely do that. HMT doesn't check the content of the table, so as long as you have the right ids in there you can go nuts. All the HMT (and `:polymorphic` for that matter) does is set up the methods, so as long as you're careful about what you're putting where, you can get away with it. Even within the documentation, if an HMT is merely an HABTM that allows extra attributes (by being a discrete model), this can be reversed such that any model comprised of "extra attributes" can be a join model. Just add IDs!
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    3. CO@Eric, but if I put the join table in the BOOK table, don't I run into trouble if (for ex.) I have two authors who wrote that book? My Book model would have a unique entry for Book #1, given. It would then need to link to Author #1 _AS WELL AS_ Author #2, and where would the second entry go? Wouldn't the Book table entry simply have a single author_id integer key and a single topic_id key? In a HABTM you just repeat keys: i.e. 1-1, 1-2, 1-3 (for book #1 having three authors). But in my case my BOOKS table is already populated with entries, each representing a given book. ??
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