# 在开发过程中需要使用 ORM 模型将表与表的多对多关联关系使用代码描述出来。多对多关系描述有一个唯一的点就是：
# 需要添加一张单独的表去记录两张表之间的对应关系
# 定义模型及表
tb_student_course = db.Table('tb_student_course',
db.Column('student_id', db.Integer, db.ForeignKey('students.id')),
db.Column('course_id', db.Integer, db.ForeignKey('courses.id'))
)
class Student(db.Model):
__tablename__ = "students"
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(64), unique=True)
courses = db.relationship('Course', secondary=tb_student_course,
backref='student',
lazy='dynamic')
class Course(db.Model):
__tablename__ = "courses"
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(64), unique=True)
# 添加测试数据
if __name__ == '__main__':
db.drop_all()
db.create_all()
# 添加测试数据
stu1 = Student(name='张三')
stu2 = Student(name='李四')
stu3 = Student(name='王五')
cou1 = Course(name='物理')
cou2 = Course(name='化学')
cou3 = Course(name='生物')
stu1.courses = [cou2, cou3]
stu2.courses = [cou2]
stu3.courses = [cou1, cou2, cou3]
db.session.add_all([stu1, stu2, stu2])
db.session.add_all([cou1, cou2, cou3])
db.session.commit()
app.run(debug=True)
