数据表的外键和约束

1、创建外键

from exts import db
import datetime

class Article(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    title = db.Column(db.String(50), nullable=False)
    content = db.Column(db.Text)
    time = db.Column(db.DateTime, default=datetime.datetime.now)
    author_id = db.Column(db.Integer, db.ForeignKey('user.id'))

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    username = db.Column(db.String(50), unique=True, nullable=False)

2、外键约束

3、使用外键约束

author_id = db.Column(db.Integer, db.ForeignKey('user.id', ondelete='SET NULL', onupdate='SET NULL'))