sqlalchemy(一)基本操作

安装

1. 需要安装MySQLdb
2. pip install sqlalchemy

安装完成后，执行

>>>import sqlalchemy >>>sqlalchemy.__version__ 

连接数据库

在sqlalchemy中，session用于创建程序与数据库之间的会话。所有对象的载入和保存都需要通过session对象。

from sqlalchemy import create_engine from sqlalchemy.orm import sessionmaker engine = create_engine('mysql://user:passwd@ip:port/db', echo=True) Session = sessionmaker(bind=engine) session = Session() session.execute('show databases') 

其中，echo为True代表打开logging。

创建一个映射

一个映射对应着一个Python类，用来表示一个表的结构。下面创建一个person表，包括id和name两个字段。

from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Person(Base): __tablename__ = 'person' id = Column(Integer, primary_key=True) name = Column(String(32)) def __repr__(self): return "<Person(name='%s')>" % self.name 

添加数据

#创建一个person对象 person = Person(name='jack') #添加person对象，但是仍然没有commit到数据库 session.add(person) #commit操作 session.commit() 

如何获取id的？

>>> person = Person(name='ilis') >>> person.id #此时还没有commit到mysql,因此无id >>> session.add(person) >>> person.id #同上 >>> session.commit() 2015-08-18 23:08:23,530 INFO sqlalchemy.engine.base.Engine INSERT INTO person (name) VALUES (%s) 2015-08-18 23:08:23,531 INFO sqlalchemy.engine.base.Engine ('ilis',) 2015-08-18 23:08:23,532 INFO sqlalchemy.engine.base.Engine COMMIT >>> person.id #commit后，可以获取该对象的id 2015-08-18 23:08:27,556 INFO sqlalchemy.engine.base.Engine BEGIN (implicit) 2015-08-18 23:08:27,557 INFO sqlalchemy.engine.base.Engine SELECT person.id AS person_id, person.name AS person_name FROM person WHERE person.id = %s 2015-08-18 23:08:27,557 INFO sqlalchemy.engine.base.Engine (5L,) 5L >>> 

添加多个数据

session.add_all([
    Person(name='jack'), Person(name='mike') ]) session.commit() 

回滚

>>> person = Person(name='test') >>> session.add(person) >>> session.query(person).filter(name=='test') >>> session.query(Person).filter(Person.name=='test').all() 2015-08-18 23:13:23,265 INFO sqlalchemy.engine.base.Engine INSERT INTO person (name) VALUES (%s) 2015-08-18 23:13:23,265 INFO sqlalchemy.engine.base.Engine ('test',) 2015-08-18 23:13:23,267 INFO sqlalchemy.engine.base.Engine SELECT person.id AS person_id, person.name AS person_name FROM person WHERE person.name = %s 2015-08-18 23:13:23,267 INFO sqlalchemy.engine.base.Engine ('test',) [<demo.Person object at 0x7f4e37730510>] >>> session.rollback() 2015-08-18 23:13:37,496 INFO sqlalchemy.engine.base.Engine ROLLBACK >>> session.query(Person).filter(Person.name=='test').all() 2015-08-18 23:13:38,690 INFO sqlalchemy.engine.base.Engine BEGIN (implicit) 2015-08-18 23:13:38,691 INFO sqlalchemy.engine.base.Engine SELECT person.id AS person_id, person.name AS person_name FROM person WHERE person.name = %s 2015-08-18 23:13:38,692 INFO sqlalchemy.engine.base.Engine ('test',) [] >>> 

数据查询

使用Session的query()方法。

#获取所有数据 session.query(Person).all() #获取某一列数据,类似于django的get,如果返回数据为多个则报错 session.query(Person).filter(Person.name=='jack').one() #获取返回数据的第一行 session.query(Person).first() #过滤数据 session.query(Person.name).filter(Person.id>1).all() #limit session.query(Person).all()[1:3] #order by session.query(Person).ordre_by(-Person.id) #equal/like/in query = session.query(Person) query.filter(Person.id==1).all() query.filter(Person.id!=1).all() query.filter(Person.name.like('%ac%')).all() query.filter(Person.id.in_([1,2,3])).all() query.filter(~Person.id.in_([1,2,3])).all() query.filter(Person.name==None).all() #and or from sqlalchemy import and_ query.filter(and_(Person.id==1, Person.name=='jack')).all() query.filter(Person.id==1, Person.name=='jack').all() query.filter(Person.id==1).filter(Person.name=='jack').all() from sqlalchemy import or_ query.filter(or_(Person.id==1, Person.id==2)).all() 

使用text

from sqlalchemy import text query.filter(text("id>1")).all() query.filter(Person.id>1).all() #同上 query.filter(text("id>:id")).params(id=1).all() #使用:，params来传参 query.from_statement( text("select * from person where name=:name")).\ params(name='jack').all() 

计数

Query使用count()函数来实现查询计数。

query.filter(Person.id>1).count() 

group by的用法

from sqlalchemy import func session.query(func.count(Person.name), Person.name),group_by(Person.name).all() 

实现count(*)来查询表内行数

session.query(func.count('*')).select_from(Person).scalar() session.query(func.count(Person.id)).scalar()