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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>SQLite Query Language: EXPLAIN</title><style type="text/css">body { margin: auto; font-family: "Verdana" "sans-serif"; padding: 8px 1%;}a { color: #45735f }a:visited { color: #734559 }.logo { position:absolute; margin:3px; }.tagline { float:right; text-align:right; font-style:italic; width:240px; margin:12px; margin-top:58px;}.toolbar { font-variant: small-caps; text-align: center; line-height: 1.6em; margin: 0; padding:1px 8px;}.toolbar a { color: white; text-decoration: none; padding: 6px 12px; }.toolbar a:visited { color: white; }.toolbar a:hover { color: #80a796; background: white; }.content { margin: 5%; }.content dt { font-weight:bold; }.content dd { margin-bottom: 25px; margin-left:20%; }.content ul { padding:0px; padding-left: 15px; margin:0px; }/* rounded corners */.se { background: url(images/se.png) 100% 100% no-repeat #80a796}.sw { background: url(images/sw.png) 0% 100% no-repeat }.ne { background: url(images/ne.png) 100% 0% no-repeat }.nw { background: url(images/nw.png) 0% 0% no-repeat }</style><meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head><body><div><!-- container div to satisfy validator --><a href="index.html"><img class="logo" src="images/SQLite.gif" alt="SQLite Logo" border="0"></a><div><!-- IE hack to prevent disappearing logo--></div><div class="tagline">Small. Fast. Reliable.<br>Choose any three.</div><table width=100% style="clear:both"><tr><td> <div class="se"><div class="sw"><div class="ne"><div class="nw"> <div class="toolbar"> <a href="about.html">About</a> <a href="sitemap.html">Sitemap</a> <a href="docs.html">Documentation</a> <a href="download.html">Download</a> <a href="copyright.html">License</a> <a href="news.html">News</a> <a href="http://www.sqlite.org/cvstrac/index">Developers</a> <a href="support.html">Support</a> </div></div></div></div></div></td></tr></table> <a href="lang.html"> <h2 align="center">SQL As Understood By SQLite</h2></a><h1>EXPLAIN</h1><h4><a href="syntaxdiagrams.html#sql-stmt">sql-stmt:</a></h4><blockquote> <img src="images/syntax/sql-stmt.gif"></img> </blockquote><p>An SQL statement can be preceded by the keyword "EXPLAIN" orby the phrase "EXPLAIN QUERY PLAN". Either modification causes theSQL statement to behave as a query and to return information abouthow the SQL statement would have operated if the EXPLAIN keyword orphrase had been omitted.</p><p>When the EXPLAIN keyword appears by itself it causes the statementto behave as a query that returns the sequence of <a href="opcode.html">virtual machine instructions</a> it would haveused to execute the command had the EXPLAIN keyword not been present.When the EXPLAIN QUERY PLAN phrase appears, the statement returnshigh-level information about what indices would have been used.</p><p>The output from EXPLAIN and EXPLAIN QUERY PLAN is intended forinteractive analysis and troubleshooting only. The details of the output format are subject to change from one release of SQLite to the next.Applications should not use EXPLAIN or EXPLAIN QUERY PLAN sincetheir behavior is undocumented, unspecified, and variable.</p><hr><small><i>This page last modified 2009/01/02 16:47:13 UTC</i></small></div></body></html>⌨️ 快捷键说明
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