标签：size rom ESS keyword option int second 跨表 result
ORM框架本质: 让面向对象的类跟数据库中的表做个对应关系
ORM与原生SQL比较：
Python ORM框架：SQLALchemy、Django、Storm、SQLObject
SQLALchemy与Django比较：
SQLALchemy框架：
SQLALchemy本身无法操作数据库，需要依赖pymysql第三方模块，Dialect用于和数据API进行交流，根据配置文件的不同调用不同的数据库API，从而实现对数据库的操作
使用pymysql连接数据库格式：
mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]
1 import datetime 2 from sqlalchemy import create_engine 3 from sqlalchemy.ext.declarative import declarative_base 4 from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index 5 from sqlalchemy.orm import relationship, sessionmaker 6 from sqlalchemy.sql import text 7 8 Base = declarative_base() 9 10 11 class Users(Base): 12 """ 13 单表创建 14 """ 15 __tablename__ = ‘users‘ 16 id = Column(Integer, primary_key=True, autoincrement=True) 17 name = Column(String(32), index=True, nullable=False) 18 email = Column(String(32), unique=True) 19 ctime = Column(DateTime, default=datetime.datetime.now) 20 extra = Column(Text, nullable=True) 21 22 __table_args__ = ( 23 UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘), 24 Index(‘ix_id_name‘, ‘name‘, ‘email‘), 25 ) 26 27 28 # 一对多示例 29 class Hobby(Base): 30 __tablename__ = ‘hobby‘ 31 id = Column(Integer, primary_key=True) 32 caption = Column(String(50), nullable=True) 33 34 35 class Person(Base): 36 __tablename__ = ‘person‘ 37 id = Column(Integer, primary_key=True, autoincrement=True) 38 name = Column(String(32), nullable=False) 39 hobby_id = Column(Integer, ForeignKey("hobby.id")) # hobby.id 中的hobby指的是tablename 40 41 # 与生成表结构无关， 仅用于查询方便 42 hobby = relationship(‘Hobby‘, backref=‘pers‘) # 此处Hobby指的是类名 43 44 45 # 多对多示例 46 class Server(Base): 47 __tablename__ = ‘server‘ 48 id = Column(Integer, primary_key=True, autoincrement=True) 49 hostname = Column(String(64), unique=True, nullable=False) 50 51 52 class Group(Base): 53 __tablename__ = ‘group‘ 54 id = Column(Integer, primary_key=True) 55 name = Column(String(64), unique=True, nullable=False) 56 57 # 与生成表无关，仅用于查询方便 58 servers = relationship(‘Server‘, secondary=‘server2group‘, backref=‘groups‘) 59 60 61 class Server2Grouop(Base): 62 __tablename__ = ‘server2group‘ 63 id = Column(Integer, primary_key=True, autoincrement=True) 64 server_id = Column(Integer, ForeignKey(‘server.id‘)) 65 group_id = Column(Integer, ForeignKey(‘group.id‘)) 66 67 68 def init_db(): 69 """ 70 根据类创建数据库表 71 :return: 72 """ 73 engine = create_engine( 74 ‘mysql+pymysql://root:mysql@127.0.0.1:3306/t1?charset=utf8‘, 75 max_overflow=0, # 超过连接池大小后 最多创建的连接 76 pool_size=3, # 连接池大小 77 pool_timeout=10, # 连接池中没有线程最多等待时间，否则报错 78 pool_recycle=-1, # 多久对线程池进行一次连接回收 79 ) 80 Base.metadata.create_all(engine) 81 82 83 def drop_db(): 84 """ 85 根据类删除数据库表 86 :return: 87 """ 88 engine = create_engine( 89 ‘mysql+pymysql://root:mysql@127.0.0.1:3306/t1?charset=utf-8‘, 90 max_overflow=0, 91 pool_size=3, 92 pool_timeout=5, 93 pool_recycle=-1, 94 ) 95 Base.metadata.drop_all(engine)
1 from sqlalchemy import create_engine 2 from sqlalchemy.ext.declarative import declarative_base 3 from sqlalchemy.sql import text 4 5 Base = declarative_base() 6 7 # 基本增删改查示例 8 def db_action(): 9 """ 10 基本数据库操作 11 :return: 12 """ 13 engine = create_engine( 14 ‘mysql+pymysql://root:mysql@127.0.0.1:3306/t1?charset=utf8‘, 15 max_overflow=0, 16 pool_size=3, 17 pool_timeout=5, 18 pool_recycle=-1, 19 ) 20 Session = sessionmaker(bind=engine) 21 22 session = Session() 23 24 # 添加操作 25 obj1 = Users(name=‘AABB‘) 26 session.add(obj1) 27 28 session.add_all([ 29 Users(name=‘tom‘), 30 Users(name=‘lily‘), 31 Users(name=‘oobb‘), 32 ]) 33 session.commit() 34 35 # 删除操作 36 session.query(Users).filter(Users.id > 2).delete() 37 session.commit() 38 39 # 修改操作 40 session.query(Users).filter(Users.id > 0).update({"name": "110"}) 41 session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "110"}, synchronize_session=False) 42 session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate") 43 session.commit() 44 45 # 查询操作 46 r1 = session.query(Users).all() 47 r2 = session.query(Users.name.label(‘别名‘), Users.email).all() 48 r3 = session.query(Users).filter(Users.name == ‘OOBB‘).all() 49 r4 = session.query(Users).filter_by(name=‘oobb‘).all() 50 r5 = session.query(Users).filter_by(name=‘oobb‘).first() 51 r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=110, name=‘aa‘).order_by( 52 Users.id).all() 53 r7 = session.query(Users).from_statement(text("select * from users where name=:name")).params(name=‘oobb‘).all() 54 55 # 常用操作 56 # [条件查询] 57 m1 = session.query(Users).filter_by(name=‘oouu‘).all() 58 m2 = session.query(Users).filter(Users.id > 1, Users.name == ‘yyuu‘).all() 59 m3 = session.query(Users).filter(Users.id.between(1, 5, 2), Users.email == ‘cc@qq.com‘).all() 60 m4 = session.query(Users).filter(Users.id.in_([1, 2, 5])).all() 61 m5 = session.query(Users).filter(~Users.id.in_([2, 3, 4])).all() # not in 62 m6 = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name=‘aa‘))).all() 63 64 65 from sqlalchemy import and_, or_ 66 67 m7 = session.query(Users).filter(and_(Users.id > 10, Users.name == ‘oo‘)).all() 68 m8 = session.query(Users).filter(or_(Users.id < 2, Users.email==‘cc@qq.com‘)).all() 69 m9 = session.query(Users).filter( 70 or_( 71 Users.id < 3, 72 and_(Users.email==‘cc@qq.com‘, Users.name==‘cc‘), 73 Users.extra !=‘‘ 74 ) 75 ) 76 77 # 通配符 78 n = session.query(Users).filter(Users.name.like(‘m%‘)).all() 79 n1 = session.query(Users).filter(~Users.name.like(‘m%‘)).all() 80 81 # 限制 82 n2 = session.query(Users)[1:5] 83 84 # 排序 85 n3 = session.query(Users).order_by(Users.id.desc()).all() 86 n4 = session.query(Users).order_by(Users.id.desc(), Users.name.asc()).all() 87 88 # 跨表查询 89 a = session.query(Hobby, Person).filter(Hobby.id == Person.hobby_id).all() 90 a1 = session.query(Person).join(Hobby).all() 91 a2 = session.query(Person).join(Hobby, isouter=True).all() 92 93 # 组合查询 94 b = session.query(Person.name).filter(Person.id>2) 95 b1 = session.query(Hobby.caption).filter(Hobby.id<10) 96 result = b.union(b1).all() 97 result2 = b.union_all(b1).all()
标签：size rom ESS keyword option int second 跨表 result
原文地址：https://www.cnblogs.com/Will-guo/p/12294257.html
