Question

我有2张桌子：餐馆和食物，以及第3张餐馆_食物，它们存储了2张桌子之间的多对多关系

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

Answer 1

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，右表外键以外的其他列时，将使用该模式。您可以使用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：

Array

Answer 2

请查看在SQLAlchemy中配置many-to-many关系。你会想要这样的东西：

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)
    restaurants = relationship(
        "Restaurant",
        secondary=restaurant_foods,
        back_populates="foods"
    )


class Restaurant(Model):
    __tablename__ = "restaurants"

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    name = db.Column(db.String(255), nullable=False)
    foods = relationship(
        "Food",
        secondary=restaurant_foods,
        back_populates="restaurants"
    )

烧瓶sqlalchemy许多额外的领域

2 个答案: