#encoding: utf-8 from sqlalchemy import create_engine,Column,Integer,String,Float,func,and_,or_,Enum from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker from random import randint HOSTNAME = '127.0.0.1' PORT = 3306 DATABASE = 'first_sqlalchemy' USERNAME = 'root' PASSWORD = '123456' #dialect+driver://username:password@host:port/database DB_URI = "mysql+pymysql://{username}:{password}@{host}:{port}/" \ "{db}?charset=utf8".format(username=USERNAME,password=PASSWORD,host=HOSTNAME,port=PORT,db=DATABASE) engine = create_engine(DB_URI) Base = declarative_base(engine) # Session = sessionmaker(engine) # session = Session() session = sessionmaker(engine)() #Session(**local_kw) class User(Base): __tablename__ = 'user' id = Column(Integer,primary_key=True,autoincrement=True) username = Column(String(50),unique=True,nullable=False) city = Column(String(50),nullable=False) age = Column(Integer,default=0) # gender = Column(Enum('male','female','secret'),default='male') def __repr__(self): return "<User(username: %s)>"%self.username Base.metadata.drop_all() Base.metadata.create_all() user1 = User(username='小李',city='长沙',age=18) user2 = User(username='小王',city='长沙',age=18) user3 = User(username='小b',city='北京',age=18) user4 = User(username='小a',city='长沙',age=20) session.add_all([user1,user2,user3,user4]) session.commit() #寻找和李A这个人在同一个城市,并且是同年龄的人 user = session.query(User).filter(User.username=='小李').first() users = session.query(User).filter(User.city==user.city,User.age==user.age).all() print(users) #用原生sql子查询怎么实现 ''' select user.id,user.username,user.city,user.age from user, (select user.username,user.age, user.city from user where user.username='小李') as li_a where user.city = li_a.city and user.age=li_a.age; ''' #sqlalchemy 提供子查询 subquery,为什么要用它,对于复杂的查询,要用到它, # 相比能提升效率 #先写原生sql里面的,然后再写外面的 #label相当于原生sql里面的as user_sub = session.query(User.city.label('city'),User.age.label('age')).filter( User.username == '小李' ).subquery()#这里使用子查询 #c相当于column user_parent = session.query(User).\ filter(User.age==user_sub.c.age,User.city==user_sub.c.city).all() print(user_parent) """ SELECT user.id AS user_id, user.username AS user_username, user.city AS user_city, user.age AS user_age FROM user, (SELECT user.city AS city, user.age AS age FROM user WHERE user.username = %(username_1)s) AS anon_1 WHERE user.age = anon_1.age AND user.city = anon_1.city """
subquery 子查询
猜你喜欢
转载自www.cnblogs.com/wuheng-123/p/9721093.html
今日推荐
周排行