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<h1>Databases</h1>

<p>A database is an abstraction on top of an operating system's file system to

ease creating, reading, updating, and deleting persistent data. The

database storage abstraction most commonly used in Python web development is

sets of relational tables. Alternative storage abstractions are explained in

the <a class="reference external" href="../no-sql-datastore.html">NoSQL</a> section of this guide.</p>

<p>Relational databases store all data in a series of tables. Interconnections

between the tables are specified as <em>foreign keys</em>.</p>

<p>Databases storage implementations vary in complexity. SQLite, a database

included with Python, creates a single file for all data per database.

Other databases such as Oracle, PostgreSQL, and MySQL have more complicated

persistence schemes while offering additional advanced features that are

useful for web application data storage.</p>

<p><a class="reference external" href="http://www.postgresql.org/">PostgreSQL</a> and

<a class="reference external" href="http://www.mysql.com/">MySQL</a> are two of the most common open source

databases.</p>

<p><a class="reference external" href="http://www.sqlite.org/">SQLite</a> is a database that is stored in a single

file on disk. SQLite is built into Python but is only built for access

by a single connection at a time. Therefore is highly recommended to not

<a class="reference external" href="https://docs.djangoproject.com/en/dev/ref/databases/#database-is-locked-errors">run a production web application with SQLite</a>.</p>

<div class="section" id="database-connections-with-python">

<h2>Database connections with Python</h2>

<p>To work with a relational database using Python, you need to use a code

library. The most common libraries for relational databases are:</p>

<p><a class="reference external" href="http://initd.org/psycopg/">psycopg2</a> for PostgreSQL</p>

<p><a class="reference external" href="https://pypi.python.org/pypi/MySQL-python/1.2.4">MySQLdb</a> for MySQL</p>

<p><a class="reference external" href="http://cx-oracle.sourceforge.net/">cx_Oracle</a> for Oracle</p>

<p>SQLite support is built into Python 2.7+ and therefore a separate library

is not necessary. Simply &quot;import sqlite3&quot; to begin interfacing with the

single file-based database.</p>

<div class="section" id="database-third-party-services">

<h2>Database third-party services</h2>

<p>Numerous companies run scalable database servers as a hosted service.

Depending on the provider, there can be several advantages to using a

hosted database third-party service:</p>

<ol class="arabic simple">

<li>automated backups and recovery</li>

<li>tightened security configurations</li>

<li>easy vertical scaling</li>

<p><a class="reference external" href="http://aws.amazon.com/rds/">Amazon Relational Database Service (RDS)</a>

provides pre-configured MySQL and PostgreSQL instances. The instances can

be scaled to larger or smaller configurations based on storage and performance

needs.</p>

<p><a class="reference external" href="https://developers.google.com/cloud-sql/">Google Cloud SQL</a> is a service

with managed, backed up, replicated, and auto-patched MySQL instances. Cloud

SQL integrates with Google App Engine but can be used independently as well.</p>

<div class="section" id="database-resources">

<h2>Database resources</h2>

<p><a class="reference external" href="http://db-engines.com/en/ranking">DB-Engines</a> ranks the most popular

database management systems.</p>

<p><a class="reference external" href="http://postgresweekly.com/">PostgreSQL Weekly</a> is a weekly newsletter of

PostgreSQL content from around the web.</p>

<p><a class="reference external" href="http://dbweekly.com/">DB Weekly</a> is a new (as of Feb 2014) weekly roundup

of general database articles and resources.</p>

<br/>

Next read the

<a href="/wsgi-servers.html">wsgi servers</a> section.

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<a href="/introduction.html" class="list-group-item ">Introduction</a>

<a href="/servers.html" class="list-group-item ">Servers</a>

<a href="/operating-systems.html" class="list-group-item ">Operating Systems</a>

<a href="/web-servers.html" class="list-group-item ">Web Servers</a>

<a href="/platform-as-a-service.html" class="list-group-item ">Platform-as-a-service</a>

<a href="/databases.html" class="list-group-item active">Databases</a>

<a href="/wsgi-servers.html" class="list-group-item ">WSGI Servers</a>

<a href="/web-frameworks.html" class="list-group-item ">Web Frameworks</a>

<a href="/task-queues.html" class="list-group-item ">Task Queues</a>

<a href="/static-content.html" class="list-group-item ">Static Content</a>

<a href="/caching.html" class="list-group-item ">Caching</a>

<a href="/web-browsers.html" class="list-group-item ">Web Browsers</a>

<a href="/web-application-security.html" class="list-group-item ">Web Application Security</a>

<a href="/monitoring.html" class="list-group-item ">Monitoring</a>

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<a href="/api-integration.html" class="list-group-item ">API Integration</a>

<a href="/source-control.html" class="list-group-item ">Source Control</a>

<a href="/configuration-management.html" class="list-group-item ">Configuration Management</a>

<a href="/dependency-management.html" class="list-group-item ">Application Dependencies</a>

<a href="/no-sql-datastore.html" class="list-group-item ">NoSQL Data Stores</a>

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