8.11 数据库ORM(5)

2018-8-11 20:43:52

昨天从俺弟家回来了.

和俺弟聊天发现,他一直停留在自己目前的圈子,自己觉得很牛逼,比别人高人一等,,

读书无用论,,可以用 幸存者偏激理论 大概就是这个 可以否决,,

越努力,越幸运!

每个人选择不同,追求的东西不同!

ORM参考  https://www.cnblogs.com/wupeiqi/articles/5713330.html

明天看数据库的最后一节 然后进入前端知识,,然后可以愉快的Django啦!!

睡觉睡觉!!2018-8-11 21:38:27  cf已经不大好完了,多花点时间看书!!!! 要把百年孤独看完,和苏东坡传!!!

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

 Base = declarative_base()

 # 创建单表
 """
 1   白金
 2   黑金
 obj.xx ==> [obj,obj...]
 """
 class UserType(Base):
     __tablename__ = 'usertype'
     id = Column(Integer, primary_key=True, autoincrement=True)
     title = Column(VARCHAR(32), nullable=True, index=True)

 """
 1   方少伟   1
 2   成套     1
 3   小白     2
 # 正向
 ut = relationship（backref='xx'）
 obj.ut ==> 1   白金
 """
 class Users(Base):
     __tablename__ = 'users'
     id = Column(Integer, primary_key=True, autoincrement=True)
     name = Column(VARCHAR(32), nullable=True, index=True)
     email = Column(VARCHAR(16), unique=True)
     user_type_id = Column(Integer,ForeignKey("usertype.id"))

     user_type = relationship("UserType",backref='xxoo')
     # __table_args__ = (
     #     UniqueConstraint('id', 'name', name='uix_id_name'),
     #     Index('ix_n_ex','name', 'email',),
     # )

 def create_db():
     engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/s4day62db?charset=utf8", max_overflow=5)
     Base.metadata.create_all(engine)

 def drop_db():
     engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/s4day62db?charset=utf8", max_overflow=5)
     Base.metadata.drop_all(engine)

 engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/s4day62db?charset=utf8", max_overflow=5)
 # 取一个连接 来连接用户
 Session = sessionmaker(bind=engine)
 session = Session()

 # 类 -> 表
 # 对象 -> 行
 # ###### 增加 ######
 #
 # obj1 = UserType(title='普通用户')
 # session.add(obj1)

 # objs =[
 #   UserType(title='超级用户'),
 #   UserType(title='白金用户'),
 #   UserType(title='黑金用户'),
 # ]
 # session.add_all(objs)

 # ###### 查 ######
 # print(session.query(UserType))
 # user_type_list = session.query(UserType).all()
 # for row in user_type_list:
 #     print(row.id,row.title)

 # select xxx  UserType where
 # user_type_list = session.query(UserType.id,UserType.title).filter(UserType.id > 2)
 # for row in user_type_list:
 #     print(row.id,row.title)

 # 分组，排序，连表，通配符，子查询，limit，union,where,原生SQL、
 # ret = session.query(Users, UserType)
 # select * from user,usertype;
 #
 # ret = session.query(Users, UserType).filter(Users.usertype_id==UserType.id)
 # select * from user,usertype whre user.usertype_id = usertype.id

 # result = session.query(Users).join(UserType)
 # print(result)

 # result = session.query(Users).join(UserType,isouter=True)
 # print(result)

 #

 # 1.
 # select * from b where id in (select id from tb2)

 # 加上  .subquery()   设置为子查询

 # 2 select * from (select * from tb) as B
 # q1 = session.query(UserType).filter(UserType.id > 0).subquery()
 # result = session.query(q1).all()
 # print(result)

 #
 # select
 #   id ,
 #   (select * from users where users.user_type_id=usertype.id)
 # from usertype;

 # session.query(UserType,session.query(Users).filter(Users.id == 1).subquery())
 # session.query(UserType,Users)
 # result = session.query(UserType.id,session.query(Users).as_scalar())
 # print(result)
 # result = session.query(UserType.id,session.query(Users).filter(Users.user_type_id==UserType.id).as_scalar())
 # print(result)

 # 问题1. 获取用户信息以及与其关联的用户类型名称(FK,Relationship=>正向操作)
 # user_list = session.query(Users,UserType).join(UserType,isouter=True)
 # print(user_list)
 # for row in user_list:
 #     print(row[0].id,row[0].name,row[0].email,row[0].user_type_id,row[1].title)

 # user_list = session.query(Users.name,UserType.title).join(UserType,isouter=True).all()
 # for row in user_list:
 #     print(row[0],row[1],row.name,row.title)

 # user_list = session.query(Users)
 # for row in user_list:
 #     print(row.name,row.id,row.user_type.title)

 # 问题2. 获取用户类型
 # type_list = session.query(UserType)
 # for row in type_list:
 #     print(row.id,row.title,session.query(Users).filter(Users.user_type_id == row.id).all())

 # type_list = session.query(UserType)
 # for row in type_list:
 #     print(row.id,row.title,row.xxoo)

 # ###### 删除 ######
 # session.query(UserType.id,UserType.title).filter(UserType.id > 2).delete()

 # ###### 修改 ######
 # session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({"title" : "黑金"})
 # session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({UserType.title: UserType.title + "x"}, synchronize_session=False)
 # session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({"num": Users.num + 1}, synchronize_session="evaluate")

 session.commit()
 session.close()