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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: CREATE INDEX</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. 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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>SQL As Understood By SQLite</h2></a><h3>CREATE INDEX</h3><table cellpadding="10"><tr><td align="right" valign="top"><i><font color="#ff3434">sql-statement</font></i> ::=</td><td><b><font color="#2c2cf0">CREATE </font></b>[<b><font color="#2c2cf0">UNIQUE</font></b>]<b><font color="#2c2cf0"> INDEX </font></b>[<b><font color="#2c2cf0">IF NOT EXISTS</font></b>]<b><font color="#2c2cf0"> </font></b>[<b><font color="#2c2cf0"></font></b><i><font color="#ff3434">database-name</font></i><b><font color="#2c2cf0"> <big>.</big></font></b>]<b><font color="#2c2cf0"> </font></b><i><font color="#ff3434">index-name</font></i><b><font color="#2c2cf0"> <br>ON </font></b><i><font color="#ff3434">table-name</font></i><b><font color="#2c2cf0"> <big>(</big> </font></b><i><font color="#ff3434">column-name</font></i><b><font color="#2c2cf0"> </font></b>[<b><font color="#2c2cf0"><big>,</big> </font></b><i><font color="#ff3434">column-name</font></i><b><font color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"></font></b><big>*</big><b><font color="#2c2cf0"> <big>)</big></font></b></td></tr><tr><td align="right" valign="top"><i><font color="#ff3434">column-name</font></i> ::=</td><td><b><font color="#2c2cf0"></font></b><i><font color="#ff3434">name</font></i><b><font color="#2c2cf0"> </font></b>[<b><font color="#2c2cf0"> COLLATE </font></b><i><font color="#ff3434">collation-name</font></i><b><font color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"> </font></b>[<b><font color="#2c2cf0"> ASC </font></b><big>|</big><b><font color="#2c2cf0"> DESC </font></b>]<b><font color="#2c2cf0"></font></b></td></tr></table><p>The CREATE INDEX command consists of the keywords "CREATE INDEX" followedby the name of the new index, the keyword "ON", the name of a previouslycreated table that is to be indexed, and a parenthesized list of names ofcolumns in the table that are used for the index key.</p><p>Each column name can be followed by one of the "ASC" or "DESC" keywordsto indicate sort order. The sort order may or may not be ignored dependingon the database file format. The "legacy" file format ignores indexsort order. The descending index file format takes index sort orderinto account. Only copies of SQLite newer than <a href="releaselog/3_3_0.html">version 3.3.0</a> (released on 2006-01-10) are able to understand the newer descendingindex file format and so for compatibility with older versions ofSQLite, the legacy file format is generated by default. Use the<a href="pragma.html#pragma_legacy_file_format">legacy_file_format</a> pragma to modify this behavior and generatedatabases that use the newer file format. Future versions of SQLitemay begin to generate the newer file format by default.</p><p>The COLLATE clause following each column name defines a collatingsequence used for text entires in that column. The default collatingsequence is the collating sequence defined for that column in the<a href="lang_createtable.html">CREATE TABLE</a> statement. Or if no collating sequence is otherwise defined,the built-in BINARY collating sequence is used.</p><p>There are no arbitrary limits on the number of indices that can beattached to a single table. The number of columns in an index is limited to <a href="limits.html#max_column">SQLITE_MAX_COLUMN</a>.</p><p>If the UNIQUE keyword appears between CREATE and INDEX then duplicateindex entries are not allowed. Any attempt to insert a duplicate entrywill result in an error. For the purposes of unique indices, all NULL valuesare considered to different from all other NULL values and are thus unique.</p><p>The textof each CREATE INDEX statement is stored in the <b>sqlite_master</b>or <b>sqlite_temp_master</b> table, depending on whether the tablebeing indexed is temporary. Every time the database is opened,all CREATE INDEX statementsare read from the <b>sqlite_master</b> table and used to regenerateSQLite's internal representation of the index layout.</p><p>If the optional IF NOT EXISTS clause is present and another indexwith the same name aleady exists, then this command becomes a no-op.</p><p>Indexes are removed with the <a href="lang_dropindex.html">DROP INDEX</a> command.</p><hr><small><i>This page last modified 2008/04/27 17:48:52 UTC</i></small></div></body></html>⌨️ 快捷键说明
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