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Query to delete orphan records [SOLVED]


Psycho

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I have three table with the following pertinent fields:

[movies]
- movie_id
- movie_name

[genres]
- genre_id
- genre_name

[movie_genres]
- movie_id
- genre_id

Now, if I have a genre that is associated with only one movie and then modify the movie to no longer be associated with the genre, I want to run a query to delete the orphan genre. In other words I need to delete records from the 'genres' table where the 'genre_id' does not exist in the 'movies_genres' table. How would I create that query?

$sql = "DELETE FROM genres WHERE ????";
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