Question

例如，我有2个模特：一个是学生，另一个是老师我是否必须在构造函数self.teacher_id = teacher_id中添加到Student？

class Student(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.Text)
    age = db.Column(db.Integer)
    teacher_id = db.Column(db.Integer, db.ForeignKey('teacher.id'))
    def __init__(self, name, age):
        self.name = name
        self.age = age

class Teacher(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    subject = db.Column(db.Text)
    students = db.relationship('Student', backref='person', lazy='dynamic')
    def __init__(self, subject):
        self.subject = subject

Answer 1

由于一个学生有很多老师，一个老师有很多学生，因此它是一个多对多的关系，你需要添加一个关联表来做到这一点：

class Student(db.Model):
    __tablename__ = 'student'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.Text)
    age = db.Column(db.Integer)
    teachers = db.relationship('Teacher', secondary='xtable', backref=db.backref('students', lazy='dynamic'))

class Teacher(db.Model):
    __tablename__ = 'teacher'
    id = db.Column(db.Integer, primary_key=True)
    subject = db.Column(db.Text)

class Xtable(db.Model):
    __tablename__ = 'xtable'
    student_id = db.Column('student_id', db.ForeignKey('student.id'))
    teacher_id = db.Column('teacher_id', db.ForeignKey('teacher.id'))

现在您应该可以查询Student.teachers和Teacher.students

了

文档：http://docs.sqlalchemy.org/en/latest/orm/basic_relationships.html#many-to-many

*请注意，当使用backref参数而不是relationship.back_populates时，backref将自动使用相同的辅助参数作为反向关系。因此，您不必将关系语句放在两个类中

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1 个答案: