从SQL转换为SQLAlchemy

Question

i have the following sql script.

SELECT *
FROM movies
LEFT JOIN possession
ON movies.id = possession.movie_id
AND possession.master_id = ?
WHERE possession.id is NULL
ORDER BY movies.id DESC

and need help to illustrate in sqlalchemy. Please can someone help me?

The following doesn't work:

movies = movie.Movie.query.join(possession.Possession, movie.Movie.id == possession.Possession.movie_id)\
            .filter(possession.Possession.master_id == session.get('userId'))\
            .filter(not_(possession.Possession.id)).order_by(movie.Movie.id.desc()).all()

Thank you very much!

Cheers

Answer 1

The most direct way to translate your SQL query is the ORM query below:

qry = (session.query(Movie)
        .outerjoin(Possession, and_(Movie.id == Possession.movie_id, Possession.master_id == master_id))
        .filter(Possession.id == None)
        .order_by(desc(Movie.id))
        )
movies = qry.all()

produces:

SELECT movies.id AS movies_id, movies.name AS movies_name
FROM movies LEFT OUTER JOIN possessions ON movies.id = possessions.movie_id AND possessions.master_id = :master_id_1
WHERE possessions.id IS NULL ORDER BY movies.id DESC

I also think this would be the faster implementation compared to an alternative of using any (see below), which is more concise, but the SQL it produces is not. This also assumes there is a relationship Movie.possessions = relationship(Possession) :

qry = (session.query(Movie)
        .filter(~Movie.possessions.any(Possession.master_id == master_id))
        .order_by(desc(Movie.id))
        )
movies = qry.all()

produces:

SELECT movies.id AS movies_id, movies.name AS movies_name
FROM movies
WHERE NOT (EXISTS (SELECT 1
FROM possessions
WHERE movies.id = possessions.movie_id AND possessions.master_id = :master_id_1)) ORDER BY movies.id DESC