SQLAlchemy实现排序有三种方式
一:order_by:查询的时候使用此方式根据某个字段或模型下的属性进行排序
二:模型定义的时候,指定排序方式
三:一对多的时候,relationship的order_by参数
准备工作
from sqlalchemy import create_engine, Column, Integer, String, Float, Text, ForeignKeyfrom sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy.orm import sessionmaker, relationship, backref # 数据库信息host = ‘127.0.0.1‘port = ‘3306‘database = ‘db_to_sqlalchemy‘username = ‘root‘password = ‘123456‘ # 数据库类型+连接数据库的插件,这里使用的pymysqlDB_URI = f‘mysql+pymysql://{username}:{password}@{host}:{port}/{database}‘ engine = create_engine(DB_URI) # 创建引擎Base = declarative_base(engine) # 使用declarative_base创建基类session = sessionmaker(engine)()
class Article(Base): __tablename__ = ‘article‘ id = Column(Integer, primary_key=True, autoincrement=True) title = Column(String(50), nullable=False) create_time = Column(DateTime, nullable=False, default=datetime.now) def __repr__(self): return f‘title: {self.title}、create_time: {self.create_time}‘ Base.metadata.drop_all() # 删除所有表Base.metadata.create_all() # 创建表 article1 = Article(title=‘title1‘)session.add(article1)session.commit()time.sleep(1)article2 = Article(title=‘title2‘)session.add(article2)session.commit()
一:order_by:查询的时候使用此方式根据某个字段或模型下的属性进行排序
默认升序
倒序:desc()
或者使用sqlalchemy.desc
二:模型定义的时候,指定排序方式
升序
倒序
class Article(Base): __tablename__ = ‘article‘ id = Column(Integer, primary_key=True, autoincrement=True) title = Column(String(50), nullable=False) create_time = Column(DateTime, nullable=False, default=datetime.now) __mapper_args__ = { ‘order_by‘: create_time.desc() } def __repr__(self): return f‘title: {self.title}、create_time: {self.create_time}‘
三:一对多的时候,relationship的order_by参数
class User(Base): __tablename__ = ‘user‘ id = Column(Integer, primary_key=True, autoincrement=True) username = Column(String(50), nullable=False) class Article(Base): __tablename__ = ‘article‘ id = Column(Integer, primary_key=True, autoincrement=True) title = Column(String(50), nullable=False) create_time = Column(DateTime, nullable=False, default=datetime.now) uid = Column(Integer, ForeignKey(‘user.id‘)) author = relationship(‘User‘, backref=backref(‘article‘, order_by=create_time.desc())) # __mapper_args__ = { # ‘order_by‘: create_time # } def __repr__(self): return f‘title: {self.title}、create_time: {self.create_time}‘
升序
若未在backref中指定排序规则,则会找__mapper_args__下的排序规则
原文地址:https://www.cnblogs.com/zhongyehai/p/11827011.html
时间: 2024-08-06 03:08:33