Python--day48--ORM框架SQLAlchemy操作表

ORM框架SQLAlchemy操作表：

表结构和数据库连接：

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
 from sqlalchemy.orm import sessionmaker, relationship
 from sqlalchemy import create_engine

 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)

 Base = declarative_base()

 # 创建单表
 class Users(Base):
     __tablename__ = 'users'
     id = Column(Integer, primary_key=True)
     name = Column(String(32))
     extra = Column(String(16))

     __table_args__ = (
     UniqueConstraint('id', 'name', name='uix_id_name'),
         Index('ix_id_name', 'name', 'extra'),
     )

     def __repr__(self):
         return "%s-%s" %(self.id, self.name)

 # 一对多
 class Favor(Base):
     __tablename__ = 'favor'
     nid = Column(Integer, primary_key=True)
     caption = Column(String(50), default='red', unique=True)

     def __repr__(self):
         return "%s-%s" %(self.nid, self.caption)

 class Person(Base):
     __tablename__ = 'person'
     nid = Column(Integer, primary_key=True)
     name = Column(String(32), index=True, nullable=True)
     favor_id = Column(Integer, ForeignKey("favor.nid"))
     # 与生成表结构无关，仅用于查询方便
     favor = relationship("Favor", backref='pers')

 # 多对多
 class ServerToGroup(Base):
     __tablename__ = 'servertogroup'
     nid = Column(Integer, primary_key=True, autoincrement=True)
     server_id = Column(Integer, ForeignKey('server.id'))
     group_id = Column(Integer, ForeignKey('group.id'))
     group = relationship("Group", backref='s2g')
     server = relationship("Server", backref='s2g')

 class Group(Base):
     __tablename__ = 'group'
     id = Column(Integer, primary_key=True)
     name = Column(String(64), unique=True, nullable=False)
     port = Column(Integer, default=22)
     # group = relationship('Group',secondary=ServerToGroup,backref='host_list')

 class Server(Base):
     __tablename__ = 'server'

     id = Column(Integer, primary_key=True, autoincrement=True)
     hostname = Column(String(64), unique=True, nullable=False)

 def init_db():
     Base.metadata.create_all(engine)

 def drop_db():
     Base.metadata.drop_all(engine)

 Session = sessionmaker(bind=engine)
 session = Session()

增：

 obj = Users(name="alex0", extra='sb')
 session.add(obj)
 session.add_all([
     Users(name="alex1", extra='sb'),
     Users(name="alex2", extra='sb'),
 ])
 session.commit()

查：

 ret = session.query(Users).all()
 ret = session.query(Users.name, Users.extra).all()
 ret = session.query(Users).filter_by(name='alex').all()
 ret = session.query(Users).filter_by(name='alex').first()

 ret = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(User.id).all()

 ret = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()

删：先查后删

 session.query(Users).filter(Users.id > 2).delete()
 session.commit()

改：先查后改

 session.query(Users).filter(Users.id > 2).update({"name" : ""})
 session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + ""}, synchronize_session=False)
 session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")
 session.commit()

其他：

 #　条件
 ret = session.query(Users).filter_by(name='alex').all()
 ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()
 ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()
 ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()
 ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()
 ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all()
 from sqlalchemy import and_, or_
 ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()
 ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all()
 ret = session.query(Users).filter(
     or_(
         Users.id < 2,
         and_(Users.name == 'eric', Users.id > 3),
         Users.extra != ""
     )).all()

 # 通配符
 ret = session.query(Users).filter(Users.name.like('e%')).all()
 ret = session.query(Users).filter(~Users.name.like('e%')).all()

 # 限制
 ret = session.query(Users)[1:2]

 # 排序
 ret = session.query(Users).order_by(Users.name.desc()).all()
 ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()

 # 分组
 from sqlalchemy.sql import func

 ret = session.query(Users).group_by(Users.extra).all()
 ret = session.query(
     func.max(Users.id),
     func.sum(Users.id),
     func.min(Users.id)).group_by(Users.name).all()

 ret = session.query(
     func.max(Users.id),
     func.sum(Users.id),
     func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all()

 # 连表

 ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()

 ret = session.query(Person).join(Favor).all()

 ret = session.query(Person).join(Favor, isouter=True).all()

 # 组合
 q1 = session.query(Users.name).filter(Users.id > 2)
 q2 = session.query(Favor.caption).filter(Favor.nid < 2)
 ret = q1.union(q2).all()

 q1 = session.query(Users.name).filter(Users.id > 2)
 q2 = session.query(Favor.caption).filter(Favor.nid < 2)
 ret = q1.union_all(q2).all()