Python sqlalchemy orm 外键关联

创建外键关联 并通过relationship 互相调用

如图：

实现代码：

import sqlalchemy

# 调用链接数据库

from sqlalchemy import create_engine

# 调用基类Base

from sqlalchemy.ext.declarative import declarative_base

# 调用Column创建字段 加类型

from sqlalchemy import Column, Integer, String,DATE,ForeignKey

# 调用操作链接,反查

from sqlalchemy.orm import sessionmaker,relationship

# create_engine 链接数据库 mysql+pymysql:链接对象//用户名:密码@主机/DB

# encoding='utf-8' 链接字符集 ，echo=True 把所有信息打印出来

engine = create_engine("mysql+pymysql://root:[email protected]/xiang",encoding='utf-8',

                       #echo=True

                       )

# 生成orm基类

Base = declarative_base()

class Student(Base):

    __tablename__ = "student"

    # 设置id为主键

    id = Column(Integer,primary_key=True)

    name = Column(String(32),nullable=False)

    register_date = Column(DATE,nullable=False)

    def __repr__(self):

        return "<%s name:%s>"%(self.id,self.name)

class StudyRecord(Base):

    __tablename__ = "study_record"

    # 设置id为主键

    id = Column(Integer,primary_key=True)

    day = Column(Integer,nullable=False)

    status = Column(String(32),nullable=False)

    # 将student表的id字段 设置为外键

    stu_id = Column(Integer,ForeignKey("student.id"))

    # -允许你在Student表里通过backref字段反向查出所有它在表里的关联项-

    # study_record表 通过student字段查找Student表内所有字段

    # student表 通过my_study_record来访问study_record表内字段

    # 注：relationship是orm自己通过在内存中类对象关联实现。

    student = relationship("Student", backref="my_study_record")

    def __repr__(self):

        return "<%s day:%s status:%s>" %(self.student.name,self.day,self.status)

#---------------1.创建表-----------------#

# 创建表结构

# Base.metadata.create_all(engine)

#---------------------------------------#

# bind=engine 绑定engine socket实例

Session_class = sessionmaker(bind=engine)

# 生成session实例，如同pymysql内的cursor

Session = Session_class()

#---------------2.插入数据-----------------#

# Student 创建插入数据

# s1 = Student(name="kevin",register_date="2014-05-21")

# s2 = Student(name="Jack",register_date="2014-05-22")

# s3 = Student(name="Rain",register_date="2014-05-23")

# s4 = Student(name="Eric",register_date="2014-05-24")

# StudyRecord 创建插入数据

# study_obj1 = StudyRecord(day=1,status="YES",stu_id=1)

# study_obj2 = StudyRecord(day=2,status="NO",stu_id=1)

# study_obj3 = StudyRecord(day=3,status="YES",stu_id=1)

# study_obj4 = StudyRecord(day=1,status="YES",stu_id=2)

# 批量插入字段数据

# Session.add_all([s1,s2,s3,s4,study_obj1,study_obj2,study_obj3,study_obj4,])

#---------------------------------------#

#---------------3.查看数据-----------------#

# 指定查看"kevin"学员

stu_obj = Session.query(Student).filter(Student.name=="kevin").first()

print(stu_obj.my_study_record)

#---------------------------------------#

# 执行事务

Session.commit()