SQLAlchemy是Python编程语言下的一款ORM框架，该框架建立在数据库API之上，使用关系对象映射进行数据库操作，简言之便是：将对象转换成SQL，然后使用数据API执行SQL并获取执行结果。
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：
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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...]更多详见：http://docs.sqlalchemy.org/en/latest/dialects/index.html |
步骤一：
使用 Engine/ConnectionPooling/Dialect 进行数据库操作，Engine使用ConnectionPooling连接数据库，然后再通过Dialect执行SQL语句。
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#!/usr/bin/env python# -*- coding:utf-8 -*-from sqlalchemy import create_engineengine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)engine.execute( "INSERT INTO ts_test (a, b) VALUES ('2', 'v1')")engine.execute( "INSERT INTO ts_test (a, b) VALUES (%s, %s)", ((555, "v1"),(666, "v1"),))engine.execute( "INSERT INTO ts_test (a, b) VALUES (%(id)s, %(name)s)", id=999, name="v1")result = engine.execute('select * from ts_test')result.fetchall() |
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine
engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)
# 事务操作
with engine.begin() as conn:
conn.execute("insert into table (x, y, z) values (1, 2, 3)")
conn.execute("my_special_procedure(5)")
conn = engine.connect()
# 事务操作
with conn.begin():
conn.execute("some statement", {'x':5, 'y':10})
注：查看数据库连接：show status like 'Threads%';
步骤二：
使用 Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 进行数据库操作。Engine使用Schema Type创建一个特定的结构对象，之后通过SQL Expression Language将该对象转换成SQL语句，然后通过 ConnectionPooling 连接数据库，再然后通过 Dialect 执行SQL，并获取结果。
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#!/usr/bin/env python# -*- coding:utf-8 -*-from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKeymetadata = MetaData()user = Table('user', metadata, Column('id', Integer, primary_key=True), Column('name', String(20)),)color = Table('color', metadata, Column('id', Integer, primary_key=True), Column('name', String(20)),)engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)metadata.create_all(engine)# metadata.clear()# metadata.remove() |
#!/usr/bin/env python # -*- coding:utf-8 -*- from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey metadata = MetaData() user = Table('user', metadata, Column('id', Integer, primary_key=True), Column('name', String(20)), ) color = Table('color', metadata, Column('id', Integer, primary_key=True), Column('name', String(20)), ) engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5) conn = engine.connect() # 创建SQL语句，INSERT INTO "user" (id, name) VALUES (:id, :name) conn.execute(user.insert(),{'id':7,'name':'seven'}) conn.close() # sql = user.insert().values(id=123, name='wu') # conn.execute(sql) # conn.close() # sql = user.delete().where(user.c.id > 1) # sql = user.update().values(fullname=user.c.name) # sql = user.update().where(user.c.name == 'jack').values(name='ed') # sql = select([user, ]) # sql = select([user.c.id, ]) # sql = select([user.c.name, color.c.name]).where(user.c.id==color.c.id) # sql = select([user.c.name]).order_by(user.c.name) # sql = select([user]).group_by(user.c.name) # result = conn.execute(sql) # print result.fetchall() # conn.close()
更多内容详见：
http://www.jianshu.com/p/e6bba189fcbd
http://docs.sqlalchemy.org/en/latest/core/expression_api.html
注：SQLAlchemy无法修改表结构，如果需要可以使用SQLAlchemy开发者开源的另外一个软件Alembic来完成。
步骤三：
使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有组件对数据进行操作。根据类创建对象，对象转换成SQL，执行SQL。
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#!/usr/bin/env python# -*- coding:utf-8 -*-from sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy import Column, Integer, Stringfrom sqlalchemy.orm import sessionmakerfrom sqlalchemy import create_engineengine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)Base = declarative_base()class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(50))# 寻找Base的所有子类，按照子类的结构在数据库中生成对应的数据表信息# Base.metadata.create_all(engine)Session = sessionmaker(bind=engine)session = Session()# ########## 增 ########### u = User(id=2, name='sb')# session.add(u)# session.add_all([# User(id=3, name='sb'),# User(id=4, name='sb')# ])# session.commit()# ########## 删除 ########### session.query(User).filter(User.id > 2).delete()# session.commit()# ########## 修改 ########### session.query(User).filter(User.id > 2).update({'cluster_id' : 0})# session.commit()# ########## 查 ########### ret = session.query(User).filter_by(name='sb').first()# ret = session.query(User).filter_by(name='sb').all()# print ret# ret = session.query(User).filter(User.name.in_(['sb','bb'])).all()# print ret# ret = session.query(User.name.label('name_label')).all()# print ret,type(ret)# ret = session.query(User).order_by(User.id).all()# print ret# ret = session.query(User).order_by(User.id)[1:3]# print ret# session.commit() |