tags = db.Table('tags',
                db.Column('tag_id', db.INTEGER, db.ForeignKey('tag.id', ondelete='CASCADE')),
                db.Column('thread_id', db.INTEGER, db.ForeignKey('article.id', ondelete='CASCADE'))
                )

# TAG Many to Many
class Tag(db.Model):
    __tablename__ = 'tag'

    id = db.Column(db.INTEGER, autoincrement=True, primary_key=True)
    name = db.Column(db.VARCHAR(30))

已经部署上去了，勉强做成这样了，在编辑的时候修改分类还有点小问题