SQLAlchemy
Posted Crazy_lyl
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介绍
SQLAlchemy是一个基于Python实现的ORM框架。该框架建立在 DB API之上,使用关系对象映射进行数据库操作,简言之便是:将类和对象转换成SQL,然后使用数据API执行SQL并获取执行结果。
安装:
pip install SQLAlchemy
组成部分:
- Engine,框架的引擎
- Connection Pooling ,数据库连接池
- Dialect,选择连接数据库的DB API种类
- Schema/Types,架构和类型
- SQL Exprression Language,SQL表达式语言
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,如:
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:http://docs.sqlalchemy.org/en/latest/dialects/index.html
使用
1.执行原生SQL
# -*- coding:utf-8 -*- # /user/bin/python # @Time : 2018/5/27 22:13 # @Author : liyongle # @File : test.py import time import threading import sqlalchemy from sqlalchemy import create_engine from sqlalchemy.engine.base import Engine engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/test?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间,否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收(重置) ) def task(arg): conn = engine.raw_connection() cursor = conn.cursor() cursor.execute( "select * from test" ) result = cursor.fetchall() cursor.close() conn.close() for i in range(20): t = threading.Thread(target=task, args=(i,)) t.start()
# -*- coding:utf-8 -*- # /user/bin/python # @Time : 2018/5/27 22:55 # @Author : liyongle # @File : new_sql.py #!/usr/bin/env python # -*- coding:utf-8 -*- import datetime from sqlalchemy import create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index from sqlalchemy.orm import relationship Base = declarative_base() # ##################### 单表示例 ######################### class Users(Base): __tablename__ = \'users\' id = Column(Integer, primary_key=True) name = Column(String(32), index=True) age = Column(Integer, default=18) email = Column(String(32), unique=True) ctime = Column(DateTime, default=datetime.datetime.now) extra = Column(Text, nullable=True) __table_args__ = ( # UniqueConstraint(\'id\', \'name\', name=\'uix_id_name\'), # Index(\'ix_id_name\', \'name\', \'extra\'), ) class Hosts(Base): __tablename__ = \'hosts\' id = Column(Integer, primary_key=True) name = Column(String(32), index=True) ctime = Column(DateTime, default=datetime.datetime.now) # ##################### 一对多示例 ######################### class Hobby(Base): __tablename__ = \'hobby\' id = Column(Integer, primary_key=True) caption = Column(String(50), default=\'篮球\') class Person(Base): __tablename__ = \'person\' nid = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=True) hobby_id = Column(Integer, ForeignKey("hobby.id")) # 与生成表结构无关,仅用于查询方便 hobby = relationship("Hobby", backref=\'pers\') # ##################### 多对多示例 ######################### class Server2Group(Base): __tablename__ = \'server2group\' id = 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) # 与生成表结构无关,仅用于查询方便 servers = relationship(\'Server\', secondary=\'server2group\', backref=\'groups\') class Server(Base): __tablename__ = \'server\' id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False) def init_db(): """ 根据类创建数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间,否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收(重置) ) Base.metadata.create_all(engine) def drop_db(): """ 根据类删除数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间,否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收(重置) ) Base.metadata.drop_all(engine) if __name__ == \'__main__\': drop_db() init_db() # 创建多个表并包含Fk、M2M关系
2.操作数据库表
#!/usr/bin/env python # -*- coding:utf-8 -*- from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from models import Users engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) ##############方式一######################## Session = sessionmaker(bind=engine) # 每次执行数据库操作时,都需要创建一个session session = Session() # ############# 执行ORM操作 ############# obj1 = Users(name="alex1") session.add(obj1) # 提交事务 session.commit() # 关闭session session.close() ######################方式二#################### # 方式二:支持线程安全,为每个线程创建一个session # - threading.Local # - 唯一标识 # ScopedSession对象 # self.registry(), 加括号 创建session # self.registry(), 加括号 创建session # self.registry(), 加括号 创建session from greenlet import getcurrent as get_ident Session = sessionmaker(bind=engine) session = scoped_session(Session,get_ident) # session.add # 操作 session.remove()
3.基本增删改查示例
# -*- coding:utf-8 -*- # /user/bin/python # @Time : 2018/5/27 22:48 # @Author : liyongle # @File : methods.py import time import threading 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 from sqlalchemy.sql import text from new_sql import Users, Hosts engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # ################ 添加 ################ """ obj1 = Users(name="wupeiqi") session.add(obj1) session.add_all([ Users(name="wupeiqi"), Users(name="alex"), Hosts(name="c1.com"), ]) session.commit() """ # ################ 删除 ################ """ session.query(Users).filter(Users.id > 2).delete() session.commit() """ # ################ 修改 ################ """ session.query(Users).filter(Users.id > 0).update({"name" : "099"}) session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False) session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate") session.commit() """ # ################ 查询 ################ """ r1 = session.query(Users).all() r2 = session.query(Users.name.label(\'xx\'), Users.age).all() r3 = session.query(Users).filter(Users.name == "alex").all() r4 = session.query(Users).filter_by(name=\'alex\').all() r5 = session.query(Users).filter_by(name=\'alex\').first() r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name=\'fred\').order_by(Users.id).all() r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name=\'ed\').all() """ session.close()
4.常用操作
# -*- coding:utf-8 -*- # /user/bin/python # @Time : 2018/5/27 22:52 # @Author : liyongle # @File : some_sql.py import time import threading 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 from sqlalchemy.sql import text from sqlalchemy.engine.result import ResultProxy from new_sql import Users, Hosts engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 查询 # cursor = session.execute(\'select * from users\') # result = cursor.fetchall() # 添加 cursor = session.execute(\'insert into users(name) values(:value)\',params={"value":\'wupeiqi\'}) session.commit() print(cursor.lastrowid) session.close() 原生SQL语句
5.常用操作
# 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()
6.基于relationship操作ForeignKey
#!/usr/bin/env python # -*- coding:utf-8 -*- import time import threading 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 from sqlalchemy.sql import text from sqlalchemy.engine.result import ResultProxy from db import Users, Hosts, Hobby, Person engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 添加 """ session.add_all([ Hobby(caption=\'乒乓球\'), Hobby(caption=\'羽毛球\'), Person(name=\'张三\', hobby_id=3), Person(name=\'李四\', hobby_id=4), ]) person = Person(name=\'张九\', hobby=Hobby(caption=\'姑娘\')) session.add(person) hb = Hobby(caption=\'男人\') hb.pers = [Person(name=\'秋凉\'), Person(name=\'\'alex\')] session.add(hb) session.commit() """ # 使用relationship正向查询 """ v = session.query(Person).first() print(v.name) print(v.hobby.caption) """ # 使用relationship反向查询 """ v = session.query(Hobby).first() print(v.caption) print(v.pers) """ session.close() 基于relationship操作ForeignKey
7.基于relationship操作m2m
#!/usr/bin/env python # -*- coding:utf-8 -*- import time import threading 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 from sqlalchemy.sql import text, func from sqlalchemy.engine.result import ResultProxy from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 关联子查询 subqry = session.query(func.count(Server.id).label("sid")).filter(Server.id == Group.id).correlate(Group).as_scalar() result = session.query(Group.name, subqry) """ SELECT `group`.name AS group_name, (SELECT count(server.id) AS sid FROM server WHERE server.id = `group`.id) AS anon_1 FROM `group` """ # 原生SQL """ # 查询 cursor = session.execute(\'select * from users\') result = cursor.fetchall() # 添加 cursor = session.execute(\'insert into users(name) values(:value)\',params={"value":\'wupeiqi\'}) session.commit() print(cursor.lastrowid) """ session.close() 其他
8. 基本增删改查补充
#!/usr/bin/env python # -*- coding:utf-8 -*- import time import threading 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 from sqlalchemy.sql import text from db import Users, Hosts engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # ################ 添加 ################ """ obj1 = Users(name="wupeiqi") session.add(obj1) #批量添加 session.add_all([ Users(name="wupeiqi"), Users(name="alex"), Hosts(name="c1.com"), ]) session.commit() """ # ################ 删除 ################ """ session.query(Users).filter(Users.id > 2).delete() session.commit() """ # ################ 修改 ################ """ session.query(Users).filter(Users.id > 0).update({"name" : "099"}) session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False) #字符串 session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate") #数字 session.commit() """ # ################ 查询 ################ """ r1 = session.query(Users).all() r2 = session.query(Users.name.label(\'xx\'), Users.age).all() #lable #as xx r3 = session.query(Users).filter(Users.name == "alex").all() r4 = session.query(Users).filter_by(name=\'alex\').all() #如果里面写条件就用filter_by,和上面filter查询是一回事,只是一种不同的方式 r5 = session.query(Users).filter_by(name=\'alex\').first() r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name=\'fred\').order_by(Users.id).all() #查询里面如果有动态传参的时候,吧它包在text里面,:value,:name这样的语法后面用.params来进行格式化 r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name=\'ed\').all() #上面的这个方式也可以用这一种 ,直接可以进行SQL语句的查询 """ session.close()
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