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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Appendix D. SQL Conformance</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="sql-keywords-appendix.html" title="Appendix C. SQL Key Words" /><link rel="next" href="features-sql-standard.html" title="D.1. Supported Features" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">Appendix D. SQL Conformance</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-keywords-appendix.html" title="Appendix C. SQL Key Words">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="appendixes.html" title="Part VIII. Appendixes">Up</a></td><th width="60%" align="center">Part VIII. Appendixes</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="features-sql-standard.html" title="D.1. Supported Features">Next</a></td></tr></table><hr></hr></div><div class="appendix" id="FEATURES"><div class="titlepage"><div><div><h2 class="title">Appendix D. SQL Conformance</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="features-sql-standard.html">D.1. Supported Features</a></span></dt><dt><span class="sect1"><a href="unsupported-features-sql-standard.html">D.2. Unsupported Features</a></span></dt><dt><span class="sect1"><a href="xml-limits-conformance.html">D.3. XML Limits and Conformance to SQL/XML</a></span></dt><dd><dl><dt><span class="sect2"><a href="xml-limits-conformance.html#FUNCTIONS-XML-LIMITS-XPATH1">D.3.1. Queries Are Restricted to XPath 1.0</a></span></dt><dt><span class="sect2"><a href="xml-limits-conformance.html#FUNCTIONS-XML-LIMITS-POSTGRESQL">D.3.2. Incidental Limits of the Implementation</a></span></dt></dl></dd></dl></div><p>
This section attempts to outline to what extent
<span class="productname">PostgreSQL</span> conforms to the current SQL
standard. The following information is not a full statement of
conformance, but it presents the main topics in as much detail as is
both reasonable and useful for users.
</p><p>
The formal name of the SQL standard is ISO/IEC 9075 <span class="quote">“<span class="quote">Database
Language SQL</span>”</span>. A revised version of the standard is released
from time to time; the most recent update appearing in 2016.
The 2016 version is referred to as ISO/IEC 9075:2016, or simply as SQL:2016.
The versions prior to that were SQL:2011, SQL:2008, SQL:2006, SQL:2003,
SQL:1999, and SQL-92. Each version
replaces the previous one, so claims of conformance to earlier
versions have no official merit.
<span class="productname">PostgreSQL</span> development aims for
conformance with the latest official version of the standard where
such conformance does not contradict traditional features or common
sense. Many of the features required by the SQL
standard are supported, though sometimes with slightly differing
syntax or function. Further moves towards conformance can be
expected over time.
</p><p>
<acronym class="acronym">SQL-92</acronym> defined three feature sets for
conformance: Entry, Intermediate, and Full. Most database
management systems claiming <acronym class="acronym">SQL</acronym> standard
conformance were conforming at only the Entry level, since the
entire set of features in the Intermediate and Full levels was
either too voluminous or in conflict with legacy behaviors.
</p><p>
Starting with <acronym class="acronym">SQL:1999</acronym>, the SQL standard defines
a large set of individual features rather than the ineffectively
broad three levels found in <acronym class="acronym">SQL-92</acronym>. A large
subset of these features represents the <span class="quote">“<span class="quote">Core</span>”</span>
features, which every conforming SQL implementation must supply.
The rest of the features are purely optional.
</p><p>
The standard versions beginning with <acronym class="acronym">SQL:2003</acronym>
are also split into a number
of parts. Each is known by a shorthand name. Note that these parts
are not consecutively numbered.
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>ISO/IEC 9075-1 Framework (SQL/Framework)</p><a id="id-1.11.5.6.2.1.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-2 Foundation (SQL/Foundation)</p><a id="id-1.11.5.6.2.2.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-3 Call Level Interface (SQL/CLI)</p><a id="id-1.11.5.6.2.3.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-4 Persistent Stored Modules (SQL/PSM)</p><a id="id-1.11.5.6.2.4.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-9 Management of External Data (SQL/MED)</p><a id="id-1.11.5.6.2.5.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-10 Object Language Bindings (SQL/OLB)</p><a id="id-1.11.5.6.2.6.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-11 Information and Definition Schemas (SQL/Schemata)</p><a id="id-1.11.5.6.2.7.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-13 Routines and Types using the Java Language (SQL/JRT)</p><a id="id-1.11.5.6.2.8.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-14 XML-related specifications (SQL/XML)</p><a id="id-1.11.5.6.2.9.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-15 Multi-dimensional arrays (SQL/MDA)</p><a id="id-1.11.5.6.2.10.2" class="indexterm"></a></li></ul></div><p>
</p><p>
The <span class="productname">PostgreSQL</span> core covers parts 1, 2, 9,
11, and 14. Part 3 is covered by the ODBC driver, and part 13 is
covered by the PL/Java plug-in, but exact conformance is currently
not being verified for these components. There are currently no
implementations of parts 4, 10, and 15
for <span class="productname">PostgreSQL</span>.
</p><p>
PostgreSQL supports most of the major features of SQL:2016. Out of
177 mandatory features required for full Core conformance,
PostgreSQL conforms to at least 170. In addition, there is a long
list of supported optional features. It might be worth noting that at
the time of writing, no current version of any database management
system claims full conformance to Core SQL:2016.
</p><p>
In the following two sections, we provide a list of those features
that <span class="productname">PostgreSQL</span> supports, followed by a
list of the features defined in <acronym class="acronym">SQL:2016</acronym> which
are not yet supported in <span class="productname">PostgreSQL</span>.
Both of these lists are approximate: There might be minor details that
are nonconforming for a feature that is listed as supported, and
large parts of an unsupported feature might in fact be implemented.
The main body of the documentation always contains the most accurate
information about what does and does not work.
</p><div class="note"><h3 class="title">Note</h3><p>
Feature codes containing a hyphen are subfeatures. Therefore, if a
particular subfeature is not supported, the main feature is listed
as unsupported even if some other subfeatures are supported.
</p></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-keywords-appendix.html" title="Appendix C. SQL Key Words">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="appendixes.html" title="Part VIII. Appendixes">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="features-sql-standard.html" title="D.1. Supported Features">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Appendix C. <acronym xmlns="http://www.w3.org/1999/xhtml" class="acronym">SQL</acronym> Key Words </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> D.1. Supported Features</td></tr></table></div></body></html>
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