我有2个表:餐厅和食物,还有第3个表Restaurants_foods,用于存储2个表之间的多对多关系
restaurants_foods = db.Table('restaurants_foods',
db.Column('restaurant_id', db.Integer, db.ForeignKey('restaurants.id'), primary_key=True),
db.Column('food_id', db.Integer, db.ForeignKey('foods.id'), primary_key=True),
db.Column('food_price', db.Float)
)
class Food(Model):
__tablename__ = "foods"
id = db.Column(db.Integer, primary_key=True, autoincrement=True)
name = db.Column(db.String(255), nullable=False)
description = db.Column(db.String(255), nullable=True)
class Restaurant(Model):
__tablename__ = "restaurants"
id = db.Column(db.Integer, primary_key=True, autoincrement=True)
name = db.Column(db.String(255), nullable=False)
foods = db.relationship('Food', secondary=restaurants_foods)
现在,当我查询Restautant.query.get(1).foods时,我希望它包含Restaurants_foods关联表中的food_price列
最佳答案
您必须使用association object模式(是多对多定义的变体):当关联表包含除左和右表的外键以外的其他列时,将使用该模式。您可以将新类直接映射到关联表,而不是使用Relationship.secondary参数。关系的左侧通过一对多引用关联对象,关联类通过多对一引用右侧。下面说明了映射到Association类的关联表,该表包括一列称为extra_data的列,该列是与父级和子级之间的每个关联一起存储的字符串值:
class Association(Base):
__tablename__ = 'association'
left_id = Column(Integer, ForeignKey('left.id'), primary_key=True)
right_id = Column(Integer, ForeignKey('right.id'), primary_key=True)
extra_data = Column(String(50))
child = relationship("Child", back_populates="parents")
parent = relationship("Parent", back_populates="children")
class Parent(Base):
__tablename__ = 'left'
id = Column(Integer, primary_key=True)
children = relationship("Association", back_populates="parent")
class Child(Base):
__tablename__ = 'right'
id = Column(Integer, primary_key=True)
parents = relationship("Association", back_populates="child")
关于python - 带额外字段的 flask sqlalchemy多对多,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35795717/