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)

# 3
# 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()