# SQLAlchemy # tutorialspoint SIMPLY EASY LEARNING  www.tutorialspoint.com ## About the Tutorial SQLAlchemy is a popular application developer. It is an open source and cross-platform software released under MIT license. SQLAlchemy is famous for its object-relational mapper (ORM), using which classes can be mapped to the database is designed for all those Python programmers who would like to understand the ORM framework with SQLAlchemy and its API. ## Prerequisites Before you start proceeding with this tutorial, we assume you have

CharField(unique=True) Model definition uses the declarative style seen in other popular ORMs like SQLAlchemy or Django. Note that we are extending the BaseModel class so the User model will inherit the database SQL levels. The idea for hybrid attributes comes from a feature of the same name in SQLAlchemy [http://docs.sqlalchemy.org/en/improve_toc/orm/extensions/hybrid.html]. Consider the following example: class "end" - "t1"."start") / 2) < 3) Pretty neat, right? Thanks for the cool idea, SQLAlchemy! ## Hybrid API class hybrid_method(func[, expr=None]) Method decorator that allows the definition

CharField(unique=True) Model definition uses the declarative style seen in other popular ORMs like SQLAlchemy or Django. Note that we are extending the BaseModel class so the User model will inherit the database Python and SQL levels. The idea for hybrid attributes comes from a feature of the same name in SQLAlchemy. Consider the following example: class Interval(Model): start = IntegerField() end = IntegerField() WHERE ((abs("t1"."end" - "t1"."start") / 2) < 3) Pretty neat, right? Thanks for the cool idea, SQLAlchemy! 230 Chapter 1. Contents: peewee Documentation, Release 3.6.0 Hybrid API class hybrid_method(func[

SQLite，它基于文件，不需要单独启动数据库服务器，适合在开发时使用，或是在数据库操作简单、访问量低的程序中使用。 ## 使用 SQLAlchemy 操作数据库 为了简化数据库操作，我们将使用 SQLAlchemy——一个 Python 数据库工具 （ORM，即对象关系映射）。借助 SQLAlchemy，你可以通过定义 Python 类来表示数据库里的一张表（类属性表示表中的字段 / 列），通过对这个类进行各种操作来代替写 使用一个叫做 Flask-SQLAlchemy 的官方扩展来集成 SQLAlchemy。 首先使用 Pipenv 安装它： $ pipenv install flask-sqlalchemy 大部分扩展都需要执行一个“初始化”操作。你需要导入扩展类，实例化并传入 Flask 程序实例： from flask_sqlalchemy import SQLAlchemy # 导入扩展类 app app = Flask(__name__) db = SQLAlchemy(app) # 初始化扩展，传入程序实例 app ## 设置数据库 URI 为了设置 Flask、扩展或是我们程序本身的一些行为，我们需要设置和定义一些配置变量。Flask 提供了一个统一的接口来写入和获取这些配置变 量：Flask.config 字典。配置变量的名称必须使用大写，写入配置的语句一般会放到扩展类实例化语句之前。

Flask作为微框架（microframework），在开发过程中会经常使用各种扩展包。以下是一些常用扩展包的简介。 - Flask-SQLAlchemy - 封装了SQLAlchemy，提供ORM - Flask-Migrate - 处理SQLAlchemy数据库的迁移（migrations） - Flask-Script - 支持在Flask里编写额外的脚本 - Flask-Bootstrap Table) ## 常见的 Python ORM • SQLAlchemy • Flask-SQLAlchemy • Django ORM • peewee ## 常见的 Python ORM • SQLAlchemy • Flask-SQLAlchemy • Django ORM • peewee ## Flask-SQLAlchemy 快速入门 from flask import Flask Flask from flask.ext.sqlAlchemy import SQLAlchemy app = Flask(__name__) app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db' db = SQLAlchemy(app) class User(db.Model):

rabbitmq.com/], but support for Redis [http://code.google.com/p/redis/] and databases (SQLAlchemy. [http://www.sqlalchemy.org/]) is also available. You may also be pleased to know that full Django integration one of the following: ☐ database (default) Use a relational database supported by SQLAlchemy. [http://sqlalchemy.org]. ☐ cache Use memcached [http://memcached.org] to store the results. ○ mongodb [http://www.sqlalchemy.org/docs/dbengine.html#supported-databases] for a table of supported databases. To use this backend you need to configure it with an Connection String [http://www.sqlalchemy.org/docs/dbengine

Documentation • Installation • Brokers • Using RabbitMQ • Using Redis • Using SQLAlchemy • Using the Django Database • Using MongoDB • Using CouchDB • Using Beanstalk MongoDB [http://mongodb.org/], CouchDB [http://couchdb.apache.org/] and databases (using SQLAlchemy [http://www.sqlalchemy.org/] or the Django ORM [http://djangoproject.com/]) is also available. Celery is easy Celery supports several message transport alternatives. • Using RabbitMQ • Using Redis • Using SQLAlchemy. • Using the Django Database • Using MongoDB • Using CouchDB • Using Beanstalk This document

Processors ○ Deploying with Setuptools ○ Deploying with Fabric ○ Using SQLite 3 with Flask ○ SQLAlchemy in Flask ○ Uploading Files • Caching View Decorators Form Validation with WTForms Template simple glue layer to the best that Python has to offer. You can implement advanced patterns in SQLAlchemy or another database tool, introduce non-relational data persistence as appropriate, and take advantage Extensions Extensions are packages that help you accomplish common tasks. For example, Flask-SQLAlchemy provides SQLAlchemy support that makes it simple and easy to use with Flask. For more on Flask extensions

Documentation • Installation • Brokers • Using RabbitMQ • Using Redis • Using SQLAlchemy • Using the Django Database • Using MongoDB • Using CouchDB • Using Beanstalk [http://aws.amazon.com/sqs/], CouchDB [http://couchdb.apache.org/] and databases (using SQLAlchemy [http://www.sqlalchemy.org/] or the Django ORM [http://djangoproject.com/]) is also available. Celery is easy Celery supports several message transport alternatives. • Using RabbitMQ • Using Redis • Using SQLAlchemy. • Using the Django Database • Using MongoDB • Using CouchDB • Using Beanstalk This document

手动管理数据库事务 - 手动将数据行（在 mysqlclient 中表示为元组 (tuple)）映射为数据对象 建议仅在需要编写复杂的SQL语句时使用驱动程序。其他情况下，建议使用ORM框架进行开发，例如SQLAlchemy、 Peewee和Django。ORM可以帮助你： - 减少管理连接和事务的模板代码 - 使用数据对象代替大量SQL语句来操作数据 ## 4.3.3.1.5 下一步 - 关于 mysqlclient mysql-connector-python 中表示为元组 (Tuple) 或者字典 (Dictionary) ）映射为数据对象 建议仅在需要编写复杂的SQL语句时使用驱动程序。其他情况下，建议使用ORM框架进行开发，例如SQLAlchemy、 Peewee和Django。ORM可以帮助你： - 减少管理连接和事务的模板代码 - 使用数据对象代替大量SQL语句来操作数据 ## 4.3.3.2.5 下一步 - 关于 mysql-connector-python ## 4.3.3.4 使用 SQLAlchemy 连接到 TiDB TiDB 是一个兼容 MySQL 的数据库。SQLAlchemy 为当前流行的开源 Python ORM (Object Relational Mapper) 之一。本文档将展示如何使用 TiDB 和 SQLAlchemy 来完成以下任务： - 配置你的环境。 - 使用 SQLAlchemy 连接到 TiDB 集群。 -