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Python中的SQL查询如何实现多表关联

sql
小樊
130
2024-08-18 13:53:40
栏目: 云计算

在Python中实现多表关联查询通常使用SQLAlchemy库来实现。SQLAlchemy是一个Python SQL工具包和对象关系映射(ORM)库,可以帮助我们轻松地进行数据库操作。

以下是一个简单的示例,展示如何使用SQLAlchemy来实现多表关联查询:

首先,需要安装SQLAlchemy库:

pip install sqlalchemy

然后,我们可以按照以下步骤实现多表关联查询:

  1. 导入必要的模块:
from sqlalchemy import create_engine, Column, Integer, String, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, relationship
  1. 创建数据库连接和Session:
# 创建数据库连接
engine = create_engine('sqlite:///database.db', echo=True)

# 创建Session
Session = sessionmaker(bind=engine)
session = Session()
  1. 创建数据库模型类:
Base = declarative_base()

class Department(Base):
    __tablename__ = 'departments'

    id = Column(Integer, primary_key=True)
    name = Column(String)

    employees = relationship('Employee', back_populates='department')

class Employee(Base):
    __tablename__ = 'employees'

    id = Column(Integer, primary_key=True)
    name = Column(String)
    department_id = Column(Integer, ForeignKey('departments.id'))

    department = relationship('Department', back_populates='employees')
  1. 创建数据库表:
Base.metadata.create_all(engine)
  1. 插入数据:
engineering = Department(name='Engineering')
session.add(engineering)

session.add(Employee(name='John Doe', department=engineering))
session.add(Employee(name='Jane Smith', department=engineering))

session.commit()
  1. 执行查询:
employees = session.query(Employee).join(Department).filter(Department.name == 'Engineering').all()

for employee in employees:
    print(employee.name, employee.department.name)

通过以上步骤,可以实现多表关联查询,并输出查询结果。希望这个示例对你有所帮助。

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