SQLAlchemy:从特定用户的favorite_series中检索所有剧集

Question

我有用户谁可以有他最喜欢的系列和有系列作为外键的剧集,我试图从最喜欢的用户系列中检索所有剧集.我正在使用Flask-SQLAlchemy.

数据库:

db = SQLAlchemy(app)

# cross table for user-series
favorite_series = db.Table('favorite_series',
    db.Column('user_id', db.Integer, db.ForeignKey('user.id')),
    db.Column('series_id', db.Integer, db.ForeignKey('series.id'))
)

# user
class User(db.Model):
    __tablename__ = 'user'
    id = db.Column(db.Integer, primary_key=True)
    favorite_series = db.relationship('Series', secondary=favorite_series,
        backref=db.backref('users', lazy='dynamic'))

# series
class Series(db.Model):
     __tablename__ = 'series'
    id = db.Column(db.Integer, primary_key=True)

# episode
class Episode(db.Model):
    __tablename__ = 'episode'
    id = db.Column(db.Integer, primary_key=True)
    series_id = db.Column(db.Integer, db.ForeignKey('series.id'))
    series = db.relationship('Series',
        backref=db.backref('episodes', lazy='dynamic'))

朋友用SQL帮助我

select user_id,series.name,episode.name from (favorite_series left join series on favorite_series.series_id = series.id) left join episode on episode.series_id = series.id where user_id=1;

尽管如此,我想在SQLAlchemy API中使用它,但无法让它运行起来.

编辑:

我的最终工作成果:

episodes = Episode.query.filter(Episode.series_id.in_(x.id for x in g.user.favorite_series)).filter(Episode.air_time!=None).order_by(Episode.air_time)

Answer 1

首先,你似乎没有声明你的表名？另外,使用orm困扰的重点是你永远不必写sql查询:

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import orm
import sqlalchemy as db
Base = declarative_base()

favorite_series = db.Table('favorite_series', Base.metadata,
    db.Column('user_id', db.Integer, db.ForeignKey('User.id')),
    db.Column('series_id', db.Integer, db.ForeignKey('Series.id'))
)
class Episode(Base):
    __tablename__ = 'Episode'
    id = db.Column(db.Integer, primary_key=True)
    season = db.Column(db.Integer)
    episode_num = db.Column(db.Integer)
    series_id = db.Column(db.Integer, db.ForeignKey('Series.id'))

    def __init__(self, season, episode_num, series_id):
        self.season = season
        self.episode_num = episode_num
        self.series_id = series_id

    def __repr__(self):
        return self.series.title + \
               ' S' + str(self.season) + \
               'E' + str(self.episode_num)

class Series(Base):
    __tablename__ = 'Series'
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String)
    episodes = orm.relationship('Episode', backref='series')

    def __init__(self, title):
        self.title = title

    def __repr__(self):
        return self.title

class User(Base):
    __tablename__ = 'User'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String)
    favorite_series = orm.relationship('Series', 
        secondary=favorite_series, backref='users')

    def __init__(self, name):
        self.name = name

    def __repr__(self):
        return self.name

现在,您只需访问对象的属性,让sql炼金术处理,让您保持数据库同步并发出查询.

engine = db.create_engine('sqlite:///:memory:')
session = orm.sessionmaker(bind=engine)()
Base.metadata.create_all(engine)

lt = User('Ludovic Tiako')
the_wire = Series('The Wire')
friends = Series('Friends')
session.add_all([lt, the_wire, friends])
session.commit() # need to commit here to generate the id fields

tw_s01e01 = Episode(1,1,the_wire.id)
tw_s01e02 = Episode(1,2,the_wire.id)
f_s01e01 = Episode(1,1,friends.id)
f_s01e02 = Episode(1,2,friends.id)
f_s01e03 = Episode(1,3,friends.id)

session.add_all([tw_s01e01, tw_s01e02, 
                f_s01e01, f_s01e02, f_s01e03])
session.commit()


the_wire.episodes # > [The Wire S1E1, The Wire S1E2]
friends.episodes # > [Friends S1E1, Friends S1E2, Friends S1E3]

最后,回答你的问题:

lt.favorite_series.append(the_wire)
session.commit()
lt.favorite_series # > [The Wire]
[s.episodes for s in lt.favorite_series] # >> [[The Wire S1E1, The Wire S1E2]]