# 53 query函数可查询的数据 1. 模型对象。指定查找这个模型中所有的对象 2. 模型中的属性。可以指定只查找某个模型的其中几个属性 3. 聚合函数 * func.count:统计行的数量 * func.avg:求平均值 * func.max:求最大值 * func.min:求最小值 * func.sum:求和 4. 'func'上，其实没有任何聚合函数，但是因为底层做了一些魔术，只要mysql中有聚合函数，都可以通过func调用 ```text 实例:session.query(func.avg(Arictle.title)).first() ``` ```text from sqlalchemy import create_engine,Column,Integer,String,DateTime,String,Float,func from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker import random HOSTNAME = '127.0.0.1' PORT = "3306" USERNAME = "root" PASSWORD = "123456" DATABASE = "xt_flask" DB_URI = "mysql+pymysql://{}:{}@{}:{}/{}?charset=utf8".format(USERNAME,PASSWORD,HOSTNAME,PORT,DATABASE) from datetime import datetime engine = create_engine(DB_URI) Base = declarative_base(engine) session = sessionmaker(engine)() class Article(Base): __tablename__ = "article" id = Column(Integer,primary_key=True,autoincrement=True) title = Column(String(50),nullable=False) price = Column(Float,nullable=False) def __repr__(self): return "<Article(title:%s)>" % self.title # Base.metadata.drop_all() # Base.metadata.create_all() # for x in range(6): # article = Article(title='title%s'%x,price=random.randint(50,100)) # print(article) # session.add(article) # session.commit() # 模型对象 # articles = session.query(Article).all() # # for article in articles: # # print(article) # print(articles) # # 模型中的属性 # articles = session.query(Article.title,Article.price).all() # print(articles) # 聚合函数 count = session.query(func.count(Article.id)).first() print(count) avg = session.query(func.avg(Article.price)).first() print(avg) max = session.query(func.max(Article.price)).first() print(max) min = session.query(func.min(Article.price)).first() print(min) sum = session.query(func.sum(Article.price)).first() print(sum) print(func.sum(Article.title)) ```