sqlalchemy的orm的多对多，正向查询，反向查询

flask的SQLAlchemy

"""
	安装：
    pip install  sqlalchemy
"""

models.py

# pip install  sqlalchemy
import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
from sqlalchemy.orm import relationship
Base = declarative_base()

class Users(Base):
    __tablename__ = 'users'  # 数据库表名称
    id = Column(Integer, primary_key=True)  # id 主键
    name = Column(String(32), index=True, nullable=False)  # name列，索引，不可为空
    age = Column(Integer)
    #email = Column(String(32), unique=True)
    #datetime.datetime.now#不能加括号，加了括号，以后永远是当前时间
    #ctime = Column(DateTime, default=datetime.datetime.now)
    #extra = Column(Text, nullable=True)

    __table_args__ = (
        # UniqueConstraint('id', 'name', name='uix_id_name'), #联合唯一
        # Index('ix_id_name', 'name', 'email'), #索引
    )

    def __repr__(self):  # 作用类似于__str__, 但是__repr__的作用更加底层，__str__则打印不出来
        return self.name


class Hobby(Base):
    __tablename__ = "hobby"
    id = Column(Integer, primary_key=True)
    catption = Column(String(50), default="双色球")


class Person(Base):
    __tablename__ = "person"
    nid = Column(Integer, primary_key=True)
    name = Column(String(32))
    #hobby指的是tablename而不是Hobby类名，
    hobby_id = Column(Integer,ForeignKey("hobby.id"))

    # 跟数据库没有关系，不会新增加字段，只能用于快速的链表查询操作
    #relationship的第一个参数，是类名，第二个参数backref，用于反向查询
    hobby =relationship("Hobby", backref="pres")

    def __repr__(self):
        return  self.name


# # 一个男孩可以喜欢多个女孩，一个女孩也可以喜欢多个男孩
class Boy2Girl(Base):
    __tablename__ = "boy2girl"
    id = Column(Integer, primary_key=True)
    girl_id = Column(Integer,ForeignKey("girl.id"))
    boy_id = Column(Integer,ForeignKey("boy.id"))


class Girl(Base):
    __tablename__ = "girl"
    id  = Column(Integer,primary_key=True)
    name =  Column(String(100),nullable=False)

    def __repr__(self):
        return self.name

class Boy(Base):
    __tablename__ = "boy"
    id = Column(Integer, primary_key=True)
    name = Column(String(100), nullable=False)
    #secondary=boy2girl 中间表的表名
    girl = relationship("Girl",secondary="boy2girl",backref = "boys")

    def __repr__(self):
        return self.name


def init_db():
    """
    根据类创建数据库表
    :return:
    """
    engine = create_engine(
        "mysql+pymysql://root:123456@127.0.0.1:3306/python13?charset=utf8",
        #"什么数据库（mysql,orcal）+用什么取链接数据库（pymysql）://数据库用户名:密码@mysqlip:端口/数据库名？charset=字符集"
        max_overflow=0,  # 超过连接池大小外最多创建的连接
        pool_size=5,  # 连接池大小
        pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错
        pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）
    )

    Base.metadata.create_all(engine)

def drop_db():
    """
    根据类删除数据库表
    :return:
    """
    engine = create_engine(
         "mysql+pymysql://root:123456@127.0.0.1:3306/python13?charset=utf8",
        max_overflow=0,  # 超过连接池大小外最多创建的连接
        pool_size=5,  # 连接池大小
        pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错
        pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）
    )

    Base.metadata.drop_all(engine)

if __name__ == '__main__':
    drop_db()
    init_db()

orm的多对多

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from models import Boy,Boy2Girl,Girl

engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/python13", max_overflow=0, pool_size=5)
Connection = sessionmaker(bind=engine)
#
# # 每次执行数据库操作时，都需要创建一个Connection
session = Connection()
#
#添加
session.add_all([
    Boy(name="tank"),
    Boy(name="sean"),
    Girl(name="仓老师"),
    Girl(name="小泽老师")
])



b2g = Boy2Girl(boy_id=1, girl_id=2)
session.add(b2g)
b2g = Boy2Girl(boy_id=2, girl_id=1)
session.add(b2g)
session.commit()
session.close()


# 正向插入
boy = Boy(name="alen")
boy.girl=[Girl(name="迪丽热巴"),Girl(name="三上悠亚")]
session.add(boy)
session.commit()

# 反向插入
girl = Girl(name="丹丹")
girl.boys=[Boy(name="吴彦祖"),Boy(name="鹿晗")]
session.add(girl)
session.commit()


# # 使用relationship的关系，正反向查

b = session.query(Boy).filter(Boy.name == "alen").first()
print(b.name)
print(b.girl)

# #反向查询
g = session.query(Girl).filter(Girl.name=="丹丹").first()
print(g.name)
print(g.boys)