Python操作MySQL之SQLAlchemy
2016-07-27 17:29
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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。
SQLAlchemy本身无法操作数据库,其必须以来pymsql等第三方插件,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.
说白了就是使用pymysql的方法一样.
add_all:增加多个
与 或:
通配符 非:
限制:
排序:
分组:
连表:
组合:
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SQLAlchemy本身无法操作数据库,其必须以来pymsql等第三方插件,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
底层处理
使用 Engine/ConnectionPooling/Dialect 进行数据库操作,Engine使用ConnectionPooling连接数据库,然后再通过Dialect执行SQL语句。#!/usr/bin/env python # -*- coding:utf-8 -*- from sqlalchemy import create_engine engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5) # 执行SQL # cur = engine.execute( # "INSERT INTO hosts (host, color_id) VALUES ('1.1.1.22', 3)" # ) # 新插入行自增ID # cur.lastrowid # 执行SQL # cur = engine.execute( # "INSERT INTO hosts (host, color_id) VALUES(%s, %s)",[('1.1.1.22', 3),('1.1.1.221', 3),] # ) # 执行SQL # cur = engine.execute( # "INSERT INTO hosts (host, color_id) VALUES (%(host)s, %(color_id)s)", # host='1.1.1.99', color_id=3 # ) # 执行SQL # cur = engine.execute('select * from hosts') # 获取第一行数据 # cur.fetchone() # 获取第n行数据 # cur.fetchmany(3) # 获取所有数据 # cur.fetchall()
说白了就是使用pymysql的方法一样.
ORM功能使用
创建表
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:7ujm8ik,@192.168.4.193:3306/testsql", 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 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')) class Group(Base): __tablename__ = 'group' id = Column(Integer, primary_key=True) name = Column(String(64), unique=True, nullable=False) class Server(Base): __tablename__ = 'server' id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False) port = Column(Integer, default=22) #定义初始化数据库函数 def init_db(): Base.metadata.create_all(engine) #顶固删除数据库函数 def drop_db(): Base.metadata.drop_all(engine) # drop_db() init_db()
操作表
操作后我们会发现,class定义的为首字母大写,写入表以后为全部小写的模式.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:7ujm8ik,@192.168.4.193:3306/testsql", 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 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')) class Group(Base): __tablename__ = 'group' id = Column(Integer, primary_key=True) name = Column(String(64), unique=True, nullable=False) class Server(Base): __tablename__ = 'server' id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False) port = Column(Integer, default=22) #定义初始化数据库函数 def init_db(): Base.metadata.create_all(engine) #顶固删除数据库函数 def drop_db(): Base.metadata.drop_all(engine) # drop_db() # init_db() #创建mysql操作对象 Session = sessionmaker(bind=engine) session = Session()
增
add:增加一个add_all:增加多个
Session = sessionmaker(bind=engine) session = Session() obj = Users(name='alex',extra='sb') session.add(obj) #add_all 列表形式 session.add_all([ Users(name='cc',extra='cow'), Users(name='dd',extra='cowcow') ]) #提交 session.commit()
删
# 删 session.query(Users).filter(Users.id > 2).delete() # 提交 session.commit()
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() # 提交 session.commit()
查
ret=session.query(Users).all() ret = session.query(Users.id, Users.extra).all() #结果为一个列表 ret = session.query(Users).filter_by(name='cc').first() ret = session.query(Users).filter_by(name='cc').all() print(type(ret)) print(ret[0].extra)
其他
条件:# 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()
与 或:
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 非:
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()
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