Flask组件之Flask-SQLAlchemy
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1、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:
pip3 install sqlalchemy
组成部分:
- Engine:框架的引擎
- Connetion 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 Expression Language:SQL表达式语言
SQLAlchemy本身无法操作数据库,其必须依赖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:
1 mysql-Python 2 mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname> 3 4 pymysql 5 mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>] 6 7 MySQL-Connector 8 mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname> 9 10 cx_Oracle 11 oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...] 12 13 更多:http://docs.sqlalchemy.org/en/latest/dialects/index.html
2、使用
2.1、执行原生SQL语句
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/t1?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 t1" ) result = cursor.fetchall() cursor.close() conn.close() for i in range(20): t = threading.Thread(target=task, args=(i,)) t.start()
#!/usr/bin/env python # -*- coding:utf-8 -*- 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/t1", max_overflow=0, pool_size=5) def task(arg): conn = engine.contextual_connect() with conn: cur = conn.execute( "select * from t1" ) result = cur.fetchall() print(result) for i in range(20): t = threading.Thread(target=task, args=(i,)) t.start()
#!/usr/bin/env python # -*- coding:utf-8 -*- import time import threading import sqlalchemy from sqlalchemy import create_engine from sqlalchemy.engine.base import Engine from sqlalchemy.engine.result import ResultProxy engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5) def task(arg): cur = engine.execute("select * from t1") result = cur.fetchall() cur.close() print(result) for i in range(20): t = threading.Thread(target=task, args=(i,)) t.start()
2.2、ORM
2.2.1、创建数据库表
#!/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 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\'), # Index(\'ix_id_name\', \'name\', \'email\'), ) 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()
#!/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()
2.2.2、操作数据库表
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 from sqlalchemy.orm import sessionmaker 4 from sqlalchemy import create_engine 5 from models import Users 6 7 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) 8 Session = sessionmaker(bind=engine) 9 10 # 每次执行数据库操作时,都需要创建一个session 11 session = Session() 12 13 # ############# 执行ORM操作 ############# 14 obj1 = Users(name="alex1") 15 session.add(obj1) 16 17 # 提交事务 18 session.commit() 19 # 关闭session 20 session.close()
#!/usr/bin/env python # -*- coding:utf-8 -*- from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session from models import Users engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) """ # 线程安全,基于本地线程实现每个线程用同一个session # 特殊的:scoped_session中有原来方法的Session中的一下方法: public_methods = ( \'__contains__\', \'__iter__\', \'add\', \'add_all\', \'begin\', \'begin_nested\', \'close\', \'commit\', \'connection\', \'delete\', \'execute\', \'expire\', \'expire_all\', \'expunge\', \'expunge_all\', \'flush\', \'get_bind\', \'is_modified\', \'bulk_save_objects\', \'bulk_insert_mappings\', \'bulk_update_mappings\', \'merge\', \'query\', \'refresh\', \'rollback\', \'scalar\' ) """ session = scoped_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()
#!/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 db import Users engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) def task(arg): session = Session() obj1 = Users(name="alex1") session.add(obj1) session.commit() for i in range(10): t = threading.Thread(target=task, args=(i,)) t.start()
#!/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) 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()
# 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()
#!/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 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()
#!/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=\'人妖\') hb.pers = [Person(name=\'文飞\'), Person(name=\'博雅\')] 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()
#!/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, 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() # 添加 """ session.add_all([ Server(hostname=\'c1.com\'), Server(hostname=\'c2.com\'), Group(name=\'A组\'), Group(name=\'B组\'), ]) session.commit() s2g = Server2Group(server_id=1, group_id=1) session.add(s2g) session.commit() gp = Group(name=\'C组\') gp.servers = [Server(hostname=\'c3.com\'),Server(hostname=\'c4.com\')] session.add(gp) session.commit() ser = Server(hostname=\'c6.com\') ser.groups = [Group(name=\'F组\'),Group(name=\'G组\')] session.add(ser) session.commit() """ # 使用relationship正向查询 """ v = session.query(Group).first() print(v.name) print(v.servers) """ # 使用relationship反向查询 """ v = session.query(Server).first() print(v.hostname) print(v.groups) """ session.close()
#!/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"以上是关于Flask组件之Flask-SQLAlchemy的主要内容,如果未能解决你的问题,请参考以下文章