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<h2>Most Widely Deployed SQL Database</h2>
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<p>We <em>believe</em> that there are more copies of SQLite
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in use around the world than any other SQL database engine,
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and possibly all other SQL database engines combined. We cannot
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be certain of this since we have no way of measuring either
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the number of SQLite deployments nor the number of deployments
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of other databases. But we believe the claim is defensible.</p>
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<p>The belief that SQLite is the most widely deployed SQL
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database engine stems from its use as an embedded database.
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Other database engines, such as MySQL, PostgreSQL, or Oracle,
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are typically found one to a server. And usually a single
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server can serve multiple users. With SQLite, on the other
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hand, a single user will typically have exclusive use of
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multiple copies of SQLite. SQLite is used on servers, but
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it is also used on desktop PC, and in cellphones, and PDAs,
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and MP3-players, and set-top boxes.</p>
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<p>At the end of 2006, there were 100 million websites on the internet.
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<a href="http://news.netcraft.com/archives/2006/11/01/november_2006_web_server_survey.html">[1]</a>
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Let us use that number as a proxy for the number of deployed
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SQL database engines other than SQLite. Not every website
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runs an SQL database engine and not every SQL database engine
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runs a website. Larger websites run multiple
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database engines. But the vast majority of smaller websites
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(the long tail) share
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a database engine with several other websites,
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if they use a database engine at all.
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And many large SQL database installations have nothing to do with
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So using the number of websites as a surrogate for the number of operational
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SQL database engines is a crude approximation, but it is the best
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we have so we will go with it. (Readers are encouraged to submit
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better estimates.)</p>
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<p>Now let's consider where SQLite is used:</p>
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<li>300 million copies of Mozilla Firefox.</li>
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<li>20 million Mac computers, each of which contains multiple
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copies of SQLite</li>
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<li>20 million websites run PHP which has SQLite built in.
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<a href="http://www.php.net/usage.php">[3]</a> We have no
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way of estimating what fraction of those sites actively use
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SQLite, but we think it is a significant fraction.</li>
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<li>450 million registered <a href="http://www.skype.com/">Skype</a> users.</li>
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<li>20 million Symbian smartphones shipped in Q3 2007
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<a href="http://www.symbian.com/news/pr/2007/pr20079552.html">[5]</a>
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Newer versions of the SymbianOS have SQLite built in. It is unclear
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exactly how many Symbian phones actually contain SQLite, so we will
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use a single quarter's sales as a lower bound.</li>
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<li>10 million Solaris 10 installations, all of which require SQLite in
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<li>Millions and millions of copies of
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<a href="http://www.mcafee.com/">McAfee</a> anti-virus software all
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use SQLite internally.</li>
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<li>Millions of iPhones use SQLite</li>
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<li>Millions and millions of other cellphones from
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manufactures other than Symbian and Apple use SQLite.
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This has not been publicly acknowledged by the manufactures
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but it is known to the SQLite developers.</li>
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<li>There are perhaps millions of additional deployments of
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SQLite that the SQLite developers do not know about.</li>
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By these estimates, we see at least 500 million SQLite deployments
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and about 100 million deployments of other SQL database engines. These
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estimates are obviously very rough and may be off significantly.
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But there is a wide margin. So the SQLite
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developers think it is likely that SQLite is the most widely deployed
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SQL database engine in the world.
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