标签：dial 转换 ini primary 一对多 back 表结构 修改 als
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，简而言之急就是：将对象转为sql，然后使用数据api执行sql并获取执行结果。
注：ORM 是一种思想 ；
SQLZlchemy本身无法操作数据库，他必须依赖pysmysql等第三插件，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
MySQL-Python mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname> pymysql mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>] MySQL-Connector mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname> cx_Oracle oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...] 更多详见：http://docs.sqlalchemy.org/en/latest/dialects/index.html
安装：
pip3 install SQLAlchemy
功能：使用所有组件对数据库进行操作，根据类创建对象，对象转换成sql，执行sql
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(VARCHAR(32)) extra = Column(VARCHAR(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(VARCHAR(50), default=‘red‘, unique=True) class Person(Base): __tablename__ = ‘person‘ nid = Column(Integer, primary_key=True) name = Column(VARCHAR(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(VARCHAR(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(VARCHAR(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)
操作表
# 创建单表 class Users(Base): __tablename__ = ‘users‘ id = Column(Integer, primary_key=True) name = Column(VARCHAR(32)) extra = Column(VARCHAR(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(VARCHAR(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()
增加
## 增加一条数据 obj = Users(name="alex0", extra=‘sb‘) session.add(obj) ## 增加多条数据 session.add_all([ Users(name="alex1", extra=‘sb‘), Users(name="alex2", extra=‘sb‘), ]) session.commit() session.close（）
查询
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()
修改
session.query(Users).filter(Users.id > 2).update({"name" : "099"}) session.commit()
删除
session.query(Users).filter(Users.id > 2).delete() session.commit()
高级操作 通配符 限制 limit 排序 分组 条件查询 链表
# 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 limit 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.min(Users.id)).group_by(Users.name).all() ret = session.query( func.max(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()
标签：dial 转换 ini primary 一对多 back 表结构 修改 als
原文地址：https://www.cnblogs.com/wyf20190411-/p/11047750.html
