Flask-SQLAlchemy , How to query many-to-many tables data

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I am using Flask-SQLalchemy trying to set up a relationship of many-to-many between two tables and here are the relationship codes.

port_trades = db.Table(
    'port_trades',
    db.Column('portfolio_id', db.Text, db.ForeignKey('portfolio.portfolio_id'), primary_key=True),
    db.Column('trade_id', db.Text, db.ForeignKey('trade.trade_id'), primary_key=True)
    )

class Portfolio(db.Model):

    __tablename__ = 'portfolio'
    user_id = db.Column(db.Text, primary_key=True)
    portfolio_id = db.Column(db.Text, primary_key=True)
    portfolio_name = db.Column(db.Text)
    trade_id = db.Column(db.Text, primary_key=True)

    trades = db.relationship('Trade', secondary=port_trades,  backref=db.backref('trades', lazy='dynamic'))

    def __repr__(self):
        return '[%r,%r,%r,%r]' % (self.user_id, self.portfolio_id, self.portfolio_name, self.trade_id)

class Trade(db.Model):
    __tablename__ = 'trade'
    trade_id = db.Column(db.Text, primary_key=True)
    user_id = db.Column(db.Text, primary_key=True)
    instrument = db.Column(db.Text)
    trade_type = db.Column(db.Text, primary_key=True)
    product_name = db.Column(db.Text)

    portfolios = db.relationship('Portfolio', secondary=port_trades, backref=db.backref('portfolios', lazy='dynamic'))

    def __repr__(self):
        return '[%r,%r,%r,%r]' % (self.trade_id, self.instrument, self. trade_type, self. product_name)

as now I can use:

port = Portfolio.query.filter_by(portfolio_id=portfolio_id).all()

to get the port with specific portfolio_id, but how can I get all the trades detail(all the properties in Trade class) from trade table.

for example these two tables like this:

-----portfolio_id ----- trade_id
          1                 2
          1                 3 
          1                 4

Thank you for your help.

flask-sqlalchemy
1 Answers

Changed few lines here and there, but feel free to change back to what you had. But do not change lazy="joined" portion as it is key to have all related objects in a query object.

port_trades = db.Table(
        'port_trades',
        db.Column('portfolio_id', db.Integer(), db.ForeignKey('portfolio.portfolio_id')),
        db.Column('trade_id', db.Integer(), db.ForeignKey('trade.trade_id'))
        )

class Portfolio(db.Model):

    __tablename__ = 'portfolio'
    user_id = db.Column(db.Text, primary_key=True)
    portfolio_id = db.Column(db.Text, primary_key=True)
    portfolio_name = db.Column(db.Text)
    trade_id = db.Column(db.Text, primary_key=True)

    def __repr__(self):
        return '[%r,%r,%r,%r]' % (self.user_id, self.portfolio_id, self.portfolio_name, self.trade_id)

class Trade(db.Model):
    __tablename__ = 'trade'
    trade_id = db.Column(db.Text, primary_key=True)
    user_id = db.Column(db.Text, primary_key=True)
    instrument = db.Column(db.Text)
    trade_type = db.Column(db.Text, primary_key=True)
    product_name = db.Column(db.Text)

    portfolios = db.relationship('Portfolio', secondary=port_trades, backref=db.backref('portfolios', lazy='joined'))

    def __repr__(self):
        return '[%r,%r,%r,%r]' % (self.trade_id, self.instrument, self. trade_type, self. product_name)

Try to use below query for querying many to many. Don't forget to put 'c'.

query_port_trades = Trade.query.join(port_trades).join(Portfolio).
filter(port_trades.c.trade_id == Trade.id and port_trades.c.portfolio_id == Portfolio.id).all()
user_47784410
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