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  • 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:

     1 #!/usr/bin/env python
     2 # -*- coding:utf-8 -*-
     3 from sqlalchemy.ext.declarative import declarative_base
     4 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
     5 from sqlalchemy.orm import sessionmaker, relationship
     6 from sqlalchemy import create_engine
     7 
     8 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)
     9 
    10 Base = declarative_base()
    11 
    12 # 创建单表
    13 class Users(Base):
    14     __tablename__ = 'users'
    15     id = Column(Integer, primary_key=True)
    16     name = Column(String(32))
    17     extra = Column(String(16))
    18 
    19     __table_args__ = (
    20     UniqueConstraint('id', 'name', name='uix_id_name'),
    21         Index('ix_id_name', 'name', 'extra'),
    22     )
    23 
    24     def __repr__(self):
    25         return "%s-%s" %(self.id, self.name)
    26 
    27 # 一对多
    28 class Favor(Base):
    29     __tablename__ = 'favor'
    30     nid = Column(Integer, primary_key=True)
    31     caption = Column(String(50), default='red', unique=True)
    32 
    33     def __repr__(self):
    34         return "%s-%s" %(self.nid, self.caption)
    35 
    36 class Person(Base):
    37     __tablename__ = 'person'
    38     nid = Column(Integer, primary_key=True)
    39     name = Column(String(32), index=True, nullable=True)
    40     favor_id = Column(Integer, ForeignKey("favor.nid"))
    41     # 与生成表结构无关,仅用于查询方便
    42     favor = relationship("Favor", backref='pers')
    43 
    44 # 多对多
    45 class ServerToGroup(Base):
    46     __tablename__ = 'servertogroup'
    47     nid = Column(Integer, primary_key=True, autoincrement=True)
    48     server_id = Column(Integer, ForeignKey('server.id'))
    49     group_id = Column(Integer, ForeignKey('group.id'))
    50     group = relationship("Group", backref='s2g')
    51     server = relationship("Server", backref='s2g')
    52 
    53 class Group(Base):
    54     __tablename__ = 'group'
    55     id = Column(Integer, primary_key=True)
    56     name = Column(String(64), unique=True, nullable=False)
    57     port = Column(Integer, default=22)
    58     # group = relationship('Group',secondary=ServerToGroup,backref='host_list')
    59 
    60 
    61 class Server(Base):
    62     __tablename__ = 'server'
    63 
    64     id = Column(Integer, primary_key=True, autoincrement=True)
    65     hostname = Column(String(64), unique=True, nullable=False)
    66 
    67 
    68 
    69 
    70 def init_db():
    71     Base.metadata.create_all(engine)
    72 
    73 
    74 def drop_db():
    75     Base.metadata.drop_all(engine)
    76 
    77 
    78 Session = sessionmaker(bind=engine)
    79 session = Session()

    增:

    1 obj = Users(name="alex0", extra='sb')
    2 session.add(obj)
    3 session.add_all([
    4     Users(name="alex1", extra='sb'),
    5     Users(name="alex2", extra='sb'),
    6 ])
    7 session.commit()

    查:

    1 ret = session.query(Users).all()
    2 ret = session.query(Users.name, Users.extra).all()
    3 ret = session.query(Users).filter_by(name='alex').all()
    4 ret = session.query(Users).filter_by(name='alex').first()
    5 
    6 ret = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(User.id).all()
    7 
    8 ret = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()

    删:先查后删

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

    改:先查后改

    1 session.query(Users).filter(Users.id > 2).update({"name" : "099"})
    2 session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False)
    3 session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")
    4 session.commit()

    其他:

     1 # 条件
     2 ret = session.query(Users).filter_by(name='alex').all()
     3 ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()
     4 ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()
     5 ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()
     6 ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()
     7 ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all()
     8 from sqlalchemy import and_, or_
     9 ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()
    10 ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all()
    11 ret = session.query(Users).filter(
    12     or_(
    13         Users.id < 2,
    14         and_(Users.name == 'eric', Users.id > 3),
    15         Users.extra != ""
    16     )).all()
    17 
    18 
    19 # 通配符
    20 ret = session.query(Users).filter(Users.name.like('e%')).all()
    21 ret = session.query(Users).filter(~Users.name.like('e%')).all()
    22 
    23 # 限制
    24 ret = session.query(Users)[1:2]
    25 
    26 # 排序
    27 ret = session.query(Users).order_by(Users.name.desc()).all()
    28 ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()
    29 
    30 # 分组
    31 from sqlalchemy.sql import func
    32 
    33 ret = session.query(Users).group_by(Users.extra).all()
    34 ret = session.query(
    35     func.max(Users.id),
    36     func.sum(Users.id),
    37     func.min(Users.id)).group_by(Users.name).all()
    38 
    39 ret = session.query(
    40     func.max(Users.id),
    41     func.sum(Users.id),
    42     func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all()
    43 
    44 # 连表
    45 
    46 ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()
    47 
    48 ret = session.query(Person).join(Favor).all()
    49 
    50 ret = session.query(Person).join(Favor, isouter=True).all()
    51 
    52 
    53 # 组合
    54 q1 = session.query(Users.name).filter(Users.id > 2)
    55 q2 = session.query(Favor.caption).filter(Favor.nid < 2)
    56 ret = q1.union(q2).all()
    57 
    58 q1 = session.query(Users.name).filter(Users.id > 2)
    59 q2 = session.query(Favor.caption).filter(Favor.nid < 2)
    60 ret = q1.union_all(q2).all()
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  • 原文地址:https://www.cnblogs.com/xudj/p/10406775.html
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