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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 Vsnapshot" /><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 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 18.4 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 /></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 2023.
  The 2023 version is referred to as ISO/IEC 9075:2023, or simply as SQL:2023.
  The versions prior to that were SQL:2016, 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 is split into a number of parts, each also known by a shorthand
  name:

  </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-1.11.5.6.1.1.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-2 Foundation (SQL/Foundation)</p><a id="id-1.11.5.6.1.2.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-3 Call Level Interface (SQL/CLI)</p><a id="id-1.11.5.6.1.3.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-4 Persistent Stored Modules (SQL/PSM)</p><a id="id-1.11.5.6.1.4.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-9 Management of External Data (SQL/MED)</p><a id="id-1.11.5.6.1.5.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-10 Object Language Bindings (SQL/OLB)</p><a id="id-1.11.5.6.1.6.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-11 Information and Definition Schemas (SQL/Schemata)</p><a id="id-1.11.5.6.1.7.2" 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-1.11.5.6.1.8.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-14 XML-related specifications (SQL/XML)</p><a id="id-1.11.5.6.1.9.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-15 Multi-dimensional arrays (SQL/MDA)</p><a id="id-1.11.5.6.1.10.2" class="indexterm"></a></li><li class="listitem"><p>ISO/IEC 9075-16 Property Graph Queries (SQL/PGQ)</p><a id="id-1.11.5.6.1.11.2" class="indexterm"></a></li></ul></div><p>

  Note that some part numbers are not (or no longer) used.
 </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, 15, and 16
  for <span class="productname">PostgreSQL</span>.
 </p><p>
  PostgreSQL supports most of the major features of SQL:2023.  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:2023.
 </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:2023</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 class="navfooter"><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 class="acronym">SQL</acronym> Key Words </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 18.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> D.1. Supported Features</td></tr></table></div></body></html>