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PORetrieving data from two chained many-to-many relationships
 

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  1. PORetrieving data from two chained many-to-many relationships
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    <p>I was practising with an example that I was creating like the one below (where I was thinking about a movie being able to belong to many categories and a category being able to belong to have many subcategories). </p> <p>Not sure if chaining two many-to-many relationships is correct (I split them up in several one to many relationships), but when I'm making a query I'm getting pretty weird results. </p> <p>Any clue how could I get movie title and genre name for all movies, even the ones without genre name? I'm using a query similar to this but it's not returning those titles :S </p> <p>If I stop after the 1st many-to-many relationship, the results seem correct but once I add the 2nd relationship (with the query below), I don't receive anything... any suggestion pls? </p> <pre><code>SELECT movie.title, genre.name FROM movie LEFT OUTER JOIN movie_genre ON (movie.movie_id = movie_genre.movie_id) JOIN genre ON (genre.genre_id = movie_genre.genre_id) JOIN genre_subgenre ON (genre_subgenre.genre_id = genre.genre_id) JOIN subgenre ON (subgenre.subgenre_id = genre_subgenre.subgenre_id) +++++++++++++++++ + Movie ID (PK) + + Movie Title + +++++++++++++++++ | | | +++++++++++++++++ + Movie ID (FK) + + Genre ID (FK) + +++++++++++++++++ | | | +++++++++++++++++++ + Genre ID (PK) + + Genre Name + +++++++++++++++++++ | | | ++++++++++++++++++++ + Genre ID (FK) + + Subgenre ID (FK) + ++++++++++++++++++++ | | | +++++++++++++++++++++++++ + Subrenre ID (PK) + + Subgenre Name (FK) + +++++++++++++++++++++++++ </code></pre>
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    1. USmickael
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    1. This table or related slice is empty.
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      1. VTUpMod
    1. COI see only threee entity and you dind't provide us tables name. Please, try to be more accurate
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      1. USDonCallisto
    2. COHave you tried other joins as LEFT OUTER JOIN?
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      1. USThit Lwin Oo
 

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