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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!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><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 12.4 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. 

  3.      Incidental Limits of the Implementation

  4.     </a></span></dt></dl></dd></dl></div><p>

  5.   This section attempts to outline to what extent

  6.   <span class="productname">PostgreSQL</span> conforms to the current SQL

  7.   standard.  The following information is not a full statement of

  8.   conformance, but it presents the main topics in as much detail as is

  9.   both reasonable and useful for users.

  10.  </p><p>

  11.   The formal name of the SQL standard is ISO/IEC 9075 <span class="quote">“<span class="quote">Database

  12.   Language SQL</span>”</span>.  A revised version of the standard is released

  13.   from time to time; the most recent update appearing in 2016.

  14.   The 2016 version is referred to as ISO/IEC 9075:2016, or simply as SQL:2016.

  15.   The versions prior to that were SQL:2011, SQL:2008, SQL:2006, SQL:2003,

  16.   SQL:1999, and SQL-92.  Each version

  17.   replaces the previous one, so claims of conformance to earlier

  18.   versions have no official merit.

  19.   <span class="productname">PostgreSQL</span> development aims for

  20.   conformance with the latest official version of the standard where

  21.   such conformance does not contradict traditional features or common

  22.   sense.  Many of the features required by the SQL

  23.   standard are supported, though sometimes with slightly differing

  24.   syntax or function.  Further moves towards conformance can be

  25.   expected over time.

  26.  </p><p>

  27.   <acronym class="acronym">SQL-92</acronym> defined three feature sets for

  28.   conformance: Entry, Intermediate, and Full.  Most database

  29.   management systems claiming <acronym class="acronym">SQL</acronym> standard

  30.   conformance were conforming at only the Entry level, since the

  31.   entire set of features in the Intermediate and Full levels was

  32.   either too voluminous or in conflict with legacy behaviors.

  33.  </p><p>

  34.   Starting with <acronym class="acronym">SQL:1999</acronym>, the SQL standard defines

  35.   a large set of individual features rather than the ineffectively

  36.   broad three levels found in <acronym class="acronym">SQL-92</acronym>.  A large

  37.   subset of these features represents the <span class="quote">“<span class="quote">Core</span>”</span>

  38.   features, which every conforming SQL implementation must supply.

  39.   The rest of the features are purely optional.  Some optional

  40.   features are grouped together to form <span class="quote">“<span class="quote">packages</span>”</span>, which

  41.   SQL implementations can claim conformance to, thus claiming

  42.   conformance to particular groups of features.

  43.  </p><p>

  44.   The standard versions beginning with <acronym class="acronym">SQL:2003</acronym>

  45.   are also split into a number

  46.   of parts.  Each is known by a shorthand name.  Note that these parts

  47.   are not consecutively numbered.

  48. 

  49.   </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></ul></div><p>

  50.  </p><p>

  51.   The <span class="productname">PostgreSQL</span> core covers parts 1, 2, 9,

  52.   11, and 14.  Part 3 is covered by the ODBC driver, and part 13 is

  53.   covered by the PL/Java plug-in, but exact conformance is currently

  54.   not being verified for these components.  There are currently no

  55.   implementations of parts 4 and 10

  56.   for <span class="productname">PostgreSQL</span>.

  57.  </p><p>

  58.   PostgreSQL supports most of the major features of SQL:2016.  Out of

  59.   179 mandatory features required for full Core conformance,

  60.   PostgreSQL conforms to at least 160.  In addition, there is a long

  61.   list of supported optional features.  It might be worth noting that at

  62.   the time of writing, no current version of any database management

  63.   system claims full conformance to Core SQL:2016.

  64.  </p><p>

  65.   In the following two sections, we provide a list of those features

  66.   that <span class="productname">PostgreSQL</span> supports, followed by a

  67.   list of the features defined in <acronym class="acronym">SQL:2016</acronym> which

  68.   are not yet supported in <span class="productname">PostgreSQL</span>.

  69.   Both of these lists are approximate: There might be minor details that

  70.   are nonconforming for a feature that is listed as supported, and

  71.   large parts of an unsupported feature might in fact be implemented.

  72.   The main body of the documentation always contains the most accurate

  73.   information about what does and does not work.

  74.  </p><div class="note"><h3 class="title">Note</h3><p>

  75.    Feature codes containing a hyphen are subfeatures.  Therefore, if a

  76.    particular subfeature is not supported, the main feature is listed

  77.    as unsupported even if some other subfeatures are supported.

  78.   </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">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="appendixes.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="features-sql-standard.html">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">Home</a></td><td width="40%" align="right" valign="top"> D.1. Supported Features</td></tr></table></div></body></html>
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