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  • SqlAlchemy

    SQLAlchemy是Python编程语言下的一款ORM框架，该框架建立在数据库API之上，使用关系对象映射进行数据库操作，简言之便是：将对象转换成SQL，然后使用数据API执行SQL并获取执行结果。

    一、安装mysql

    yum install -y mysql-server

    二、

    使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有组件对数据进行操作。根据类创建对象，对象转换成SQL，执行SQL。

    1.创建表

    #!/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'),
    )
 
 
# 一对多
class Favor(Base):
    __tablename__ = 'favor'
    nid = Column(Integer, primary_key=True)
    caption = Column(String(50), default='red', unique=True)
 
 
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"))
 
 
# 多对多
class Group(Base):
    __tablename__ = 'group'
    id = Column(Integer, primary_key=True)
    name = Column(String(64), unique=True, nullable=False)
    port = Column(Integer, default=22)
 
 
class Server(Base):
    __tablename__ = 'server'
 
    id = Column(Integer, primary_key=True, autoincrement=True)
    hostname = Column(String(64), unique=True, nullable=False)
 
 
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'))
 
 
def init_db():
    Base.metadata.create_all(engine)
 
 
def drop_db():
    Base.metadata.drop_all(engine)
    View Code

    2、操作表

     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()
    表结构 + 数据库连接
    • 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()
    View Code
    • 删
    session.query(Users).filter(Users.id > 2).delete()
session.commit()
    View Code
    • 改
    session.query(Users).filter(Users.id > 2).update({"name" : "099"})
session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False)
session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")
session.commit()
    View Code
    • 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()
    View Code
    • 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()
    View Code
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  • 原文地址：https://www.cnblogs.com/terrycy/p/6011239.html
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