Python编程：sqlalchemy模块对msyql的增删改查

安装

$ pip install sqlalchemy

初始化表

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

# 创建对象的基类
Base = declarative_base()

# 定义Student对象
class Student(Base):
    # 表的结构
    id = Column(Integer(), primary_key=True)
    name = Column(String(20))

    # 一对多
    books = relationship("Book")

    # 表的名字
    __tablename__= "student"


# 书籍
class Book(Base):
    id = Column(Integer(), primary_key=True)
    name = Column(String(20))

    # “多”的一方的book表是通过外键关联到Student表的
    stu_id = Column(Integer(), ForeignKey("student.id"))

    __tablename__ = "book"


# 初始化数据库连接，参数解决中文编码问题
engine = create_engine("mysql+pymysql://root:[email protected]/demo?charset=utf8")

# 创建数据表
Base.metadata.create_all(engine)

# 创建DBSession类型
DBSession = sessionmaker(bind=engine)

# 实例化session对象
session = DBSession()

增加

# 创建新Student对象
student1 = Student(id=1, name="小红")
student2 = Student(id=2, name="小明")

# 添加到session
session.add(student1)
session.add(student2)


# 创建书籍
book1 = Book(id=1, name="语文", stu_id=1)
book2 = Book(id=2, name="数学", stu_id=1)
book3 = Book(id=3, name="英语", stu_id=2)
session.add_all([book1, book2, book3])

# 提交即保存到数据库
session.commit()

查询

student = session.query(Student).filter(Student.id==1).first()
print(student)
# <__main__.Student object at 0x103c44400>

print(student.id)
# 1

print(student.name)
# 小红

for book in student.books:
    print(book.name)
# 语文
# 数学

修改

student = session.query(Student).filter(Student.id==1).first()
student.name = "小白"

session.commit()

删除

student = session.query(Student).filter(Student.id==2).first()
session.delete(student)

session.commit()

善后工作

# 关闭session
session.close()

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