SQLAlchemy JOIN 和不明确的列名

Question

我有这张桌子

class Domain(Base):
    __tablename__ = "domains"
    domain_id = Column(Integer(), primary_key=True)
    domain_name = Column(String(), unique=True)


class Subdomain(Base):
    __tablename__ = "subdomains"
    subdomain_id = Column(Integer(), primary_key=True)
    subdomain_name = Column(String(), unique=True)
    domain_id = Column(Integer, ForeignKey('domains.domain_id'))


class Title(Base):
    __tablename__ = "titles"
    title_id = Column(Integer(), primary_key=True)
    domain_id = Column(Integer, ForeignKey('domains.domain_id'))
    subdomain_id = Column(Integer, ForeignKey('subdomains.subdomain_id'))
    title = Column(String())
    status = Column(Integer())
    response_len = Column(Integer())
    created_on = Column(DateTime(), default=datetime.now)
    updated_on = Column(DateTime(), default=datetime.now, onupdate=datetime.now)

当我尝试这个时：

query = session.query(Domain.domain_name, Subdomain.subdomain_name, Title.title, Title.status, Title.response_len, Title.created_on, Title.updated_on)
query = query.join(Title).join(Subdomain).join(Domain)

我明白了：

ambiguous column name: domains.domain_name [SQL: 'SELECT domains.domain_name AS domains_domain_name, subdomains.subdomain_name AS subdomains_subdomain_name, titles.title AS titles_title, titles.status AS titles_status, titles.response_len AS titles_response_len, titles.created_on AS titles_created_on, titles.updated_on AS titles_updated_on \nFROM domains JOIN titles ON domains.domain_id = titles.domain_id JOIN subdomains ON subdomains.subdomain_id = titles.subdomain_id JOIN domains ON domains.domain_id = subdomains.domain_id']

最初我在域中有名称，在子域中有名称，我尝试使用标签 - 它没有帮助。我将它重命名为 domain_name 和 subdomain_name ，但仍然没有运气。

Answer 1

Domain 已作为连接中最左侧的表引入：FROM domains JOIN ...，因为它是您在查询的选择列表中选择的第一个表。显式无别名连接是不必要的，并且会导致您的错误。直接省略：

query = session.query(Domain.domain_name, Subdomain.subdomain_name, Title.title, Title.status, Title.response_len, Title.created_on, Title.updated_on)
query = query.join(Title).join(Subdomain)