Python操作MySQL之SQLAlchemy，pythonsqlalchemy

Python操作MySQL之SQLAlchemy，pythonsqlalchemy

SQLAlchemy是Python程式設計語言下的一款ORM架構，該架構建立在資料庫API之上，使用關聯性物件映射進行資料庫操作。簡言之便是：將對象轉換成SQL，然後使用資料API執行SQL並擷取執行結果，SQLAlchemy可以操作各種SQL語句。

SQLAlchemy本身無法操作資料庫，其必須以來pymsql等第三方外掛程式，Dialect用於和資料API進行交流，根據設定檔的不同調用不同的資料庫API，從而實現對資料庫的操作.

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...]  更多詳見：http://docs.sqlalchemy.org/en/latest/dialects/index.html　

底層處理

使用 Engine/ConnectionPooling/Dialect 進行資料庫操作，Engine使用ConnectionPooling串連資料庫，然後再通過Dialect執行SQL語句。

#!/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) # 執行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 # 執行SQL# cur = engine.execute(#     "INSERT INTO hosts (host, color_id) VALUES(%s, %s)",[('1.1.1.22', 3),('1.1.1.221', 3),]# )  # 執行SQL# cur = engine.execute(#     "INSERT INTO hosts (host, color_id) VALUES (%(host)s, %(color_id)s)",#     host='1.1.1.99', color_id=3# ) # 執行SQL# cur = engine.execute('select * from hosts')# 擷取第一行資料# cur.fetchone()# 擷取第n行資料# cur.fetchmany(3)# 擷取所有資料# cur.fetchall()

　　

ORM功能使用建立表from sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Indexfrom sqlalchemy.orm import sessionmaker, relationshipfrom sqlalchemy import create_engineengine = create_engine("mysql+pymysql://root:7ujm8ik,@192.168.4.193:3306/testsql", max_overflow=5)Base = declarative_base()# 建立單表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'), )# 一對多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"))# 多對多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)#定義初始化資料庫函數def init_db(): Base.metadata.create_all(engine)#頂固刪除資料庫函數def drop_db(): Base.metadata.drop_all(engine)# drop_db()init_db()建立表動作表

操作後我們會發現,class定義的為首字母大寫,寫入表以後為全部小寫的模式.

from sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Indexfrom sqlalchemy.orm import sessionmaker, relationshipfrom sqlalchemy import create_engineengine = create_engine("mysql+pymysql://root:7ujm8ik,@192.168.4.193:3306/testsql", max_overflow=5)Base = declarative_base()# 建立單表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'), )# 一對多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"))# 多對多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)#定義初始化資料庫函數def init_db(): Base.metadata.create_all(engine)#頂固刪除資料庫函數def drop_db(): Base.metadata.drop_all(engine)# drop_db()# init_db()#建立mysql操作對象Session = sessionmaker(bind=engine)session = Session()動作表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()#add 增加一個#add_all 增加多個增# 刪session.query(Users).filter(Users.id > 2).delete()# 提交session.commit()刪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()改ret=session.query(Users).all()ret = session.query(Users.id, Users.extra).all() #結果為一個列表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)查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()條件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()非ret = session.query(Users).filter(Users.name.like('e%')).all()ret = session.query(Users).filter(~Users.name.like('e%')).all()與，或，非限制: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()分組:from sqlalchemy.sql import funcret = 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()限制，排序和分組連表: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()組合: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()連表與組合

摘自

http://www.cnblogs.com/ccorz/p/5711955.html