python之SQLAlchemy组件
介绍
SQLAlchemy 是一个 ORM 框架，可以帮助我们使用面向对象的方式快速实现数据库操作。
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，其必须依赖 pymysql 等第三方插件，Dialect（方言）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：
MySQLDB 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
安装
pip3 install sqlalchemy
创建和删除表
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) age = Column(Integer, nullable=False) name = Column(String(32), index=True, nullable=False) """ 根据类创建数据库表 """ engine = create_engine( "mysql+pymysql://root:root@127.0.0.1:3306/1221?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 init_db(): # 创建表 Base.metadata.create_all(engine) def drop_db(): Base.metadata.drop_all(engine) if __name__ == '__main__': drop_db() init_db()
单表操作
from sqlalchemy.orm import sessionmaker 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)
age = Column(Integer, nullable=False) name = Column(String(32), index=True, nullable=False) engine = create_engine("mysql+pymysql://root:root@127.0.0.1:3306/1221", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) # 每次执行数据库操作时，都需要创建一个session session = Session()
# 添加单条 obj = Users(name="zhangsan",age=20) session.add(obj) # 添加多条 obj1 = Users(name='lisi',age=12) obj2 = Users(name='wangwu',age=14) session.add_all([obj1, obj2]) # 提交事务 session.commit()
# 查询所有 user_query = session.query(Users) print(user_query) # SELECT users.id AS users_id, users.name AS users_name FROM users print(user_query.all()) # [<__main__.Users object at 0x0000000003A3E2B0>, <__main__.Users object at 0x0000000003A3E320>, <__main__.Users object at 0x0000000003A3E390>] # 过滤条件 user_query = user_query.filter(Users.id > 1) print(user_query) # SELECT users.id AS users_id, users.name AS users_name FROM users WHERE users.id > %(id_1)s print(user_query.all()) # [<__main__.Users object at 0x000000000395E4A8>, <__main__.Users object at 0x000000000395E518>] # 取第一个 print(user_query.first()) # <__main__.Users object at 0x000000000392DC88>
# 删除 返回删除条数 print(session.query(Users).filter(Users.id > 1).delete()) # 2 session.commit()
# 修改方式一 user_obj = session.query(Users).filter(Users.id == 1).first() user_obj.name = '张大三' session.commit() # 修改方式二 session.query(Users).filter(Users.id == 1).update({Users.name: '张小三'}) session.commit() # 在原来值基础修改 session.query(Users).filter(Users.id == 1).update({Users.name: Users.name + '1'}, synchronize_session=False) session.query(Users).filter(Users.id == 1).update({'age': Users.age + 2}, synchronize_session='evaluate') session.commit()
# 通过字段过滤 session.query(Users).filter_by(name='zhangsan').all() # filter 中过滤多条件时它们的关系是 and session.query(Users).filter(Users.id > 1, Users.name == 'lisi').all() # between session.query(Users).filter(Users.id.between(1,2)).all() # in session.query(Users).filter(Users.id.in_([1, 3])).all() # not in session.query(Users).filter(~Users.id.in_([1, 3])).all() # 子查询 session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='zhangsan'))).all() # and 和 or 操作 from sqlalchemy import and_, or_ session.query(Users).filter(and_(Users.id > 3, Users.name == 'lisi')).all() session.query(Users).filter(or_(Users.id < 2, Users.name == 'zhangsan')).all() session.query(Users).filter( or_( Users.id < 2, and_(Users.name == 'zhangsan', Users.id > 3), )).all() # like session.query(Users).filter(Users.name.like('z%')).all() # not like session.query(Users).filter(~Users.name.like('z%')).all() # 切片 含首不含尾 session.query(Users)[0:1] # order by session.query(Users).order_by(Users.name).all() # order by desc session.query(Users).order_by(Users.name.desc(),Users.id.asc()).all() # group by & having & max & sum & min & avg from sqlalchemy.sql import func session.query(func.max(Users.age), func.sum(Users.age), func.min(Users.age), func.avg(Users.age)).group_by(Users.age).having(func.min(Users.age) > 14).all() # [(26, Decimal('26'), 26, Decimal('26.0000'))] # 查询指定列 & as ret = session.query(Users.name,Users.age,Users.name.label('nick_name')).all() [print(user_item[0],user_item.age,user_item.nick_name) for user_item in ret] # 连表 # where xx.id = xx.id session.query(Users, Favor).filter(Users.id == Favor.nid).all() # inner join session.query(Person).join(Favor).all() # outer join 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) # 合并去重 ret = q1.union(q2).all() # 合并不去重 ret = q1.union_all(q2).all()
一对多操作
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 Depart(Base): __tablename__ = 'depart' id = Column(Integer, primary_key=True) title = Column(String(32), nullable=True) class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) dept_id = Column(Integer, ForeignKey('depart.id')) """ 根据类创建数据库表 """ engine = create_engine( "mysql+pymysql://root:root@127.0.0.1:3306/1221?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 init_db(): # 创建表 Base.metadata.create_all(engine) def drop_db(): Base.metadata.drop_all(engine) if __name__ == '__main__': drop_db() init_db()
from sqlalchemy.orm import sessionmaker 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 Depart(Base): __tablename__ = 'depart' id = Column(Integer, primary_key=True) title = Column(String(32), nullable=True) class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) dept_id = Column(Integer, ForeignKey('depart.id')) engine = create_engine("mysql+pymysql://root:root@127.0.0.1:3306/1221", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) # 每次执行数据库操作时，都需要创建一个session session = Session()
# 查询所有用户名称 & 所属部门名称 user_list = session.query(Users, Depart).join(Depart, Users.dept_id == Depart.id).all() print(user_list) ''' [(<__main__.Users object at 0x000000000395C8D0>, <__main__.Depart object at 0x000000000395C940>), (<__main__.Users object at 0x000000000395C9B0>, <__main__.Depart object at 0x000000000395C940>), (<__main__.Users object at 0x000000000395CA20>, <__main__.Depart object at 0x000000000395CA90>)] ''' [print(user[0].name, user[1].title) for user in user_list] ''' 张三 后勤部 李四 后勤部 王五 财务部 ''' # SELECT users.name AS users_name, depart.title AS depart_title FROM users INNER JOIN depart ON users.dept_id = depart.id user_list = session.query(Users.name, Depart.title).join(Depart, Users.dept_id == Depart.id).all() print(user_list, type(user_list)) # [('张三', '后勤部'), ('李四', '后勤部'), ('王五', '财务部')] [print(user.name, user.title) for user in user_list] ''' 张三 后勤部 李四 后勤部 王五 财务部 ''' # SELECT users.name AS users_name, depart.title AS depart_title FROM users LEFT OUTER JOIN depart ON users.dept_id = depart.id user_list = session.query(Users.name, Depart.title).join(Depart, Users.dept_id == Depart.id, isouter=True) print(user_list)
# 正向查询 ：查询所有用户关联的部门名称 user_list = session.query(Users).all() [print(user.name, user.depart, user.depart.title) for user in user_list] ''' 张三 <__main__.Depart object at 0x00000000039697F0> 后勤部 李四 <__main__.Depart object at 0x00000000039697F0> 后勤部 王五 <__main__.Depart object at 0x0000000003969898> 财务部 ''' # 反向查询 ：查询后勤部所有用户名称 depart_obj = session.query(Depart).filter_by(id=1).first() [print(user.name, user) for user in depart_obj.users] ''' 张三 <__main__.Users object at 0x000000000395FA20> 李四 <__main__.Users object at 0x000000000395F978> ''' # 关联新增 ：创建一个部门'酱油部'，再在该部门中添加一个员工'李德刚' # 方式一： user_obj = Users(name='李德刚') depart_obj = Depart(title='酱油部', users=[user_obj]) session.add(depart_obj) session.commit() # 方式二： depart_obj = Depart(title='酱油部') user_obj = Users(name='李德刚', depart=depart_obj) session.add(user_obj) session.commit()
多对多操作
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 Permission(Base): '''权限''' __tablename__ = 'permission' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) class User(Base): '''用户''' __tablename__ = 'user' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) class Permission2User(Base): __tablename__ = 'permission2user' id = Column(Integer, primary_key=True, autoincrement=True) user_id = Column(Integer, ForeignKey('user.id')) permission_id = Column(Integer, ForeignKey('permission.id')) __table_args__ = ( # 联合唯一索引 UniqueConstraint('user_id', 'permission_id', name='uc_user_permission'), ) """ 根据类创建数据库表 """ engine = create_engine( "mysql+pymysql://root:root@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 init_db(): # 创建表 Base.metadata.create_all(engine) def drop_db(): Base.metadata.drop_all(engine) if __name__ == '__main__': drop_db() init_db()
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 sessionmaker, relationship Base = declarative_base() class Permission(Base): '''权限''' __tablename__ = 'permission' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) # 第一个参数：指定关联的模型类，secondary ：指定通过该表创建多对多关系，backref ：反向查询时字段 user_list = relationship('User', secondary='permission2user', backref='permission_list') class User(Base): '''用户''' __tablename__ = 'user' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) class Permission2User(Base): __tablename__ = 'permission2user' id = Column(Integer, primary_key=True, autoincrement=True) user_id = Column(Integer, ForeignKey('user.id')) permission_id = Column(Integer, ForeignKey('permission.id')) __table_args__ = ( # 联合唯一索引 UniqueConstraint('user_id', 'permission_id', name='uc_user_permission'), ) engine = create_engine("mysql+pymysql://root:root@127.0.0.1:3306/test", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session()
# 初始化数据 session.add_all( [ Permission(name='新增'), Permission(name='查询'), User(name='张三'), User(name='吴刚') ] ) session.commit() session.add_all([ Permission2User(user_id=1,permission_id=1), Permission2User(user_id=1,permission_id=2), Permission2User(user_id=2,permission_id=2), ]) session.commit()
list = session.query(Permission2User.id, User.name, Permission.name) \ .join(Permission, Permission2User.permission_id == Permission.id) \ .join(User, Permission2User.user_id == User.id).all() print(list) # [(3, '吴刚', '查询'), (1, '张三', '新增'), (2, '张三', '查询')] # 查询拥有新增权限的用户 permission_obj = session.query(Permission).filter_by(name='新增').first() [print(user_obj.name) for user_obj in permission_obj.user_list] # 张三 # 查询吴刚拥有的权限 user_obj = session.query(User).filter_by(name='吴刚').first() [print(permission_obj.name) for permission_obj in user_obj.permission_list] # 查询 # 创建一个权限，再创建两个用户，让这两个用户拥有这个权限 permission_obj = Permission(name='修改') permission_obj.user_list = [User(name='王五'), User(name='赵柳')] session.add(permission_obj) session.commit()
两种连接方式
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 sessionmaker, relationship, scoped_session Base = declarative_base() class User(Base): '''用户''' __tablename__ = 'user' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) engine = create_engine("mysql+pymysql://root:root@127.0.0.1:3306/test", max_overflow=0, pool_size=5) SessionFactory = sessionmaker(bind=engine) def task1(): # 去连接池获取一个连接。 session = SessionFactory() ret = session.query(User).all() # 将连接交还给连接池。 session.close() session = scoped_session(session_factory=SessionFactory) def task2(): # 当真正使用 session 时，才从连接池中取一个连接放在 threading.Local 对象的当前线程域中，实现多线程访问时的 session 隔离。 ret = session.query(User).all() # 将连接交还给连接池 session.remove() from threading import Thread for i in range(20): t1 = Thread(target=task1) t1.start() t2 = Thread(target=task2) t2.start()
执行原生Sql
# 添加 cursor = session.execute('insert into user(name) values(:name)', params={"name": '刘能'}) session.commit() print(cursor.lastrowid) # 5 # 查询 cursor = session.execute('select * from user') result = cursor.fetchall() print(result) # [(5, '刘能'), (2, '吴刚'), (1, '张三'), (3, '王五'), (4, '赵柳')]
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