databases.html

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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>
<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>
</ol>
<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>
<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>
</div>

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