如何使用 SQLAlchemy 核心进行自动连接？

Posted 2023-02-16

【中文标题】如何使用 SQLAlchemy 核心进行自动连接？

【英文标题】：How to do an automatic join using SQLAlchemy core?

【发布时间】：2021-02-10 22:29:39

【问题描述】：

我在代表我的数据库的 sqlalchemy 中有以下 ORM 架构，我希望自动加入来自客户的发票。

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
from sqlalchemy import Column, ForeignKey, Integer, String

Base = declarative_base()


class Customer(Base):
    __tablename__ = 'customers'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    address = Column(String)
    email = Column(String)
    invoices = relationship("Invoice", primaryjoin="Customer.id == Invoice.custid")


class Invoice(Base):
    __tablename__ = 'invoices'
    id = Column(Integer, primary_key=True)
    custid = Column(Integer, ForeignKey("customers.id"))
    invno = Column(Integer)
    amount = Column(Integer)

如果我使用这种说法：

s = session.query(Customer, Invoice).join(Customer.invoices)

它给了我正确的结果：

SELECT customers.id AS customers_id, customers.name AS customers_name, customers.address AS customers_address, customers.email AS customers_email, invoices.id AS invoices_id, invoices.custid AS invoices_custid, invoices.invno AS invoices_invno, invoices.amount AS invoices_amount FROM customers JOIN invoices ON customers.id = invoices.custid

但是我想使用 SQL Alchemy 的核心，使用 Select、Join，没有查询，我该怎么做呢？

我试过了：

j = Customer.join(Customer.invoices)
stmt = select([Customer,Invoice]).select_from(j)

但不工作，有什么想法吗？

提前致谢。

【参考方案1】：

结果是：

s = select([Customer, Invoice]).select_from(join(Customer, Invoice))