sqlalchemy学习笔记

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外键

    class User(db.Model):        __tablename__ = 'users'        id = db.Column(db.Integer, primary_key=True)        name = db.Column(db.String(20), nullable=False)    def __init__(self, name):        self.name = name    class Article(db.Model):        __tablename__ = 'articles'        id = db.Column(db.Integer, primary_key=True)        title = db.Column(db.String(50), nullable=False)        content = db.Column(db.Text, nullable=False)        author_id = db.Column(db.Integer, db.ForeignKey('users.id'))        author = db.relationship('User', backref=db.backref('articles'))        def __init__(self, title, content):            self.title = title            self.content = content

多对多

Article_tag = db.Table(    'article_tag',    db.Column('article_id', db.Integer, db.ForeignKey('articles.id'), primary_key=True),    db.Column('tag_id', db.Integer, db.ForeignKey('tags.id'), primary_key=True))class Article(db.Model):    __tablename__ = 'articles'    id = db.Column(db.Integer, primary_key=True, autoincrement=True)    title = db.Column(db.String(20), nullable=False)    content = db.Column(db.Text, nullable=False)    tags = db.relationship(        'Tag',        secondary=Article_tag,        backref=db.backref('tags', lazy='dynamic'),  # 动态        lazy='dynamic'  # 动态    )    def __init__(self, title, content):        self.title = title        self.content = contentclass Tag(db.Model):    __tablename__ = 'tags'    id = db.Column(db.Integer, primary_key=True, autoincrement=True)    name = db.Column(db.String(20), nullable=False)    articles = db.relationship(        'Article',        secondary=Article_tag,        backref=db.backref('articles', lazy='dynamic'),  # 动态        lazy='dynamic'  # 动态    )    def __init__(self, name):        self.name = name

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