SQLAlchemy
1.1.SQLAlchemy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
1.2.SQLAlchemy表结构
（1）创建单表
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 Base = declarative_base() class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) 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'), #id和name联合唯一 Index('ix_id_name', 'name', 'email'), #索引 ) 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()
（2）创建多个表（包含FK，M2M关系）
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): '''爱好''' __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")) #hobby指的__tablename__ = 'hobby'，而不是类名Hobby # 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 ######################### #第三张表要自己生成 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:123456@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） ) 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()
实例：
models.py
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): '''爱好''' __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")) #hobby指的__tablename__ = 'hobby'，而不是类名Hobby # 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 ######################### #第三张表要自己生成 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) if __name__ == '__main__': engine = create_engine( "mysql+pymysql://root:123456@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） ) Base.metadata.create_all(engine) #创建 # Base.metadata.drop_all(engine) #删除
1.3.SQLAlchemy两种连接方式
第一种
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine import models #1.创建连接池 engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) #2.从连接池中获取数据库连接 session = Session() #3.执行ORM操作 obj1 = models.Users(name="derek",email='derek@163.com') session.add(obj1) # 提交事务 session.commit() # 4.关闭数据库连接(将连接放回连接池) session.close()
第二种、基于scoped_session实现线程安全
首先导入，然后只要修改session = scoped_session(Session)
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session import models #1.创建连接池 engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) #2.从连接池中获取数据库连接 # session = Session() session = scoped_session(Session) #3.执行ORM操作 obj1 = models.Users(name="jack",email='jack@163.com') session.add(obj1) # 提交事务 session.commit() # 4.关闭数据库连接 session.close()
1.4.增加数据
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session import models #1.创建连接池 engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) #2.从连接池中获取数据库连接 session = Session() # session = scoped_session(Session) # #3.执行ORM操作 # obj1 = models.Users(name="jack",email='jack@163.com') # session.add(obj1) # # 提交事务 # session.commit() #批量增加,里面是列表 session.add_all([ models.Users(name="jack1",email='jack1@163.com'), models.Users(name="jack2",email='jack2@163.com'), ]) session.commit() # 4.关闭数据库连接 session.close()
1.5.查看和删除数据
#查看数据 user_list = session.query(models.Users).all() for row in user_list: print(row.id) print(row.name) print(row.email) print(row.ctime)
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session import models #1.创建连接池 engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) #2.从连接池中获取数据库连接 session = Session() # session = scoped_session(Session) # #3.执行ORM操作 # obj1 = models.Users(name="jack",email='jack@163.com') # session.add(obj1) # # 提交事务 # session.commit() # #批量增加,里面是列表 # session.add_all([ # models.Users(name="jack1",email='jack1@163.com'), # models.Users(name="jack2",email='jack2@163.com'), # ]) # session.commit() #查看数据 user_list = session.query(models.Users).all() for row in user_list: print(row.id) print(row.name) print(row.email) print(row.ctime) # 4.关闭数据库连接 session.close()
查看的结果：
添加过滤条件
user_list = session.query(models.Users).filter(models.Users.id > 2) #id大于2的
删除数据
#删除数据 session.query(models.Users).filter(models.Users.id > 4).delete() session.commit()
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session import models #1.创建连接池 engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) #2.从连接池中获取数据库连接 session = Session() # session = scoped_session(Session) # #3.执行ORM操作 # obj1 = models.Users(name="jack",email='jack@163.com') # session.add(obj1) # # 提交事务 # session.commit() # #批量增加,里面是列表 # session.add_all([ # models.Users(name="jack1",email='jack1@163.com'), # models.Users(name="jack2",email='jack2@163.com'), # ]) # session.commit() #查看数据 # user_list = session.query(models.Users).all() # user_list = session.query(models.Users).filter(models.Users.id > 2) #id大于2的 # for row in user_list: # print(row.id) # print(row.name) # print(row.email) # print(row.ctime) #删除数据 session.query(models.Users).filter(models.Users.id > 4).delete() session.commit() # 4.关闭数据库连接 session.close()
1.6.修改数据
#修改数据 session.query(models.Users).filter(models.Users.id == 4).update({'name':'Tom'}) session.query(models.Users).filter(models.Users.id == 1).update({'name': models.Users.name + "099"}, synchronize_session=False) session.query(models.Users).filter(models.Users.id == 3).update({"age": models.Users.age + 1}, synchronize_session="evaluate") session.commit()
结果：
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