Flask sqlalchemy 多对多插入数据 [英] Flask sqlalchemy many-to-many insert data

问题描述

我试图在 Flask-SQLAlchemy 中建立多对多关系，但似乎我不知道如何填充多对多标识符数据库".你能帮我理解我做错了什么以及它应该是什么样子吗?

I am trying to make a many to many relation here in Flask-SQLAlchemy, but it seems that I don't know how to fill the "many to many identifier database". Could you please help me understand what I am doing wrong and how it is supposed to look?

class User(db.Model):
    __tablename__ = 'users'
    user_id = db.Column(db.Integer, primary_key=True)
    user_fistName = db.Column(db.String(64))
    user_lastName = db.Column(db.String(64))
    user_email = db.Column(db.String(128), unique=True)


class Class(db.Model):
    __tablename__ = 'classes'
    class_id = db.Column(db.Integer, primary_key=True)
    class_name = db.Column(db.String(128), unique=True)

然后是我的标识符数据库:

and then my identifier database:

student_identifier = db.Table('student_identifier',
    db.Column('class_id', db.Integer, db.ForeignKey('classes.class_id')),
    db.Column('user_id', db.Integer, db.ForeignKey('users.user_id'))
)

到目前为止，当我尝试将数据插入数据库时​​，它看起来像这样.

so far it looks like this when I try to insert the data into the database.

# User
user1 = User(
            user_fistName='John',
            user_lastName='Doe',
            user_email='[e-mail]')

user2 = User(
            user_fistName='Jack',
            user_lastName='Doe',
            user_email='[e-mail]')

user3 = User(
            user_fistName='Jane',
            user_lastName='Doe',
            user_email='[e-mail]')

db.session.add_all([user1, user2, user3])
db.session.commit()

# Class
cl1 = Class(class_name='0A')
cl2 = Class(class_name='0B')
cl3 = Class(class_name='0C')
cl4 = Class(class_name='Math')
cl5 = Class(class_name='Spanish')
db.session.add_all([cl1, cl2, cl3, cl4, cl5])
db.session.commit()

现在我的问题是，我如何添加到多对多数据库中，因为我真的无法创建一个 'student_identifier' 对象?如果可以的话，它可能看起来像这样:

Now my problem is, how do I add to the many to many database, since I really can't create a 'student_identifier' object? If I could it could perhaps have looked like this:

# Student Identifier
sti1  = StiClass(class_id=cl1.class_id, class_name=user1.user_id)
sti2  = StiClass(class_id=cl3.class_id, class_name=user1.user_id)
sti3  = StiClass(class_id=cl4.class_id, class_name=user1.user_id)
sti4  = StiClass(class_id=cl2.class_id, class_name=user2.user_id)
db.session.add_all([sti1, sti2, sti3, sti4])
db.session.commit()

我应该如何使用 ORM 插入多对多表?

How I am supposed to insert into a many to many table with ORM?

推荐答案

您不需要直接向关联表添加任何内容，SQLAlchemy 会这样做.这或多或少来自 SQLAlchemy 文档:

You don't need to add anything directly to your association table, SQLAlchemy will do that. This is more or less from SQLAlchemy documentations:

association_table = db.Table('association', db.Model.metadata,
    db.Column('left_id', db.Integer, db.ForeignKey('left.id')),
    db.Column('right_id', db.Integer, db.ForeignKey('right.id'))
)

class Parent(db.Model):
    __tablename__ = 'left'
    id = db.Column(db.Integer, primary_key=True)
    children = db.relationship("Child",
                    secondary=association_table)

class Child(db.Model):
    __tablename__ = 'right'
    id = db.Column(db.Integer, primary_key=True)


p = Parent()
c = Child()
p.children.append(c)
db.session.add(p)
db.session.commit()

因此您的样本将是这样的:

Therefore your sample would be like this:

student_identifier = db.Table('student_identifier',
    db.Column('class_id', db.Integer, db.ForeignKey('classes.class_id')),
    db.Column('user_id', db.Integer, db.ForeignKey('students.user_id'))
)

class Student(db.Model):
    __tablename__ = 'students'
    user_id = db.Column(db.Integer, primary_key=True)
    user_fistName = db.Column(db.String(64))
    user_lastName = db.Column(db.String(64))
    user_email = db.Column(db.String(128), unique=True)


class Class(db.Model):
    __tablename__ = 'classes'
    class_id = db.Column(db.Integer, primary_key=True)
    class_name = db.Column(db.String(128), unique=True)
    students = db.relationship("Student",
                               secondary=student_identifier)

s = Student()
c = Class()
c.students.append(s)
db.session.add(c)
db.session.commit()

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