案例表：
1 # coding=utf-8 2 from flask_sqlalchemy import SQLAlchemy 3 4 db = SQLAlchemy() 5 6 7 tags_class = db.Table('tags_classifications', 8 db.Column('tag_id', db.Integer, db.ForeignKey('tag.id')), 9 db.Column('classify_id', db.Integer, db.ForeignKey('classification.id')) 10 ) 11 12 class Classification(db.Model): 13 __tablename__ = 'classification' 14 id = db.Column(db.Integer, primary_key=True) 15 title = db.Column(db.String(1024), unique=True) 16 img_title = db.Column(db.String(1024)) 17 img_url = db.Column(db.String(2048)) 18 19 tags = db.relationship('Tag', secondary=tags_class, 20 backref=db.backref('classifications', lazy='dynamic')) 21 22 23 def __init__(self, title,img_title,img_url): 24 self.title = title 25 self.img_title = img_title 26 self.img_url = img_url 27 28 def __repr__(self): 29 return '<Classification %r>' % self.title 30 31 class Tag(db.Model): 32 __tablename__ = 'tag' 33 id = db.Column(db.Integer, primary_key=True) 34 name = db.Column(db.String(1024), unique=True) 35 img_title = db.Column(db.String(1024)) 36 img_url = db.Column(db.String(2048)) 37 38 39 def __init__(self, name,img_title,img_url): 40 self.name = name 41 self.img_title = img_title 42 self.img_url = img_url 43 44 def __repr__(self): 45 return '<Tag: %r>' % self.name