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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-05 17:28:19 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-05 17:28:19 +0000
commit18657a960e125336f704ea058e25c27bd3900dcb (patch)
tree17b438b680ed45a996d7b59951e6aa34023783f2 /www/rowidtable.html
parentInitial commit. (diff)
downloadsqlite3-upstream.tar.xz
sqlite3-upstream.zip
Adding upstream version 3.40.1.upstream/3.40.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<!DOCTYPE html>
+<html><head>
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
+<link href="sqlite.css" rel="stylesheet">
+<title>Rowid Tables</title>
+<!-- path= -->
+</head>
+<body>
+<div class=nosearch>
+<a href="index.html">
+<img class="logo" src="images/sqlite370_banner.gif" alt="SQLite" border="0">
+</a>
+<div><!-- IE hack to prevent disappearing logo --></div>
+<div class="tagline desktoponly">
+Small. Fast. Reliable.<br>Choose any three.
+</div>
+<div class="menu mainmenu">
+<ul>
+<li><a href="index.html">Home</a>
+<li class='mobileonly'><a href="javascript:void(0)" onclick='toggle_div("submenu")'>Menu</a>
+<li class='wideonly'><a href='about.html'>About</a>
+<li class='desktoponly'><a href="docs.html">Documentation</a>
+<li class='desktoponly'><a href="download.html">Download</a>
+<li class='wideonly'><a href='copyright.html'>License</a>
+<li class='desktoponly'><a href="support.html">Support</a>
+<li class='desktoponly'><a href="prosupport.html">Purchase</a>
+<li class='search' id='search_menubutton'>
+<a href="javascript:void(0)" onclick='toggle_search()'>Search</a>
+</ul>
+</div>
+<div class="menu submenu" id="submenu">
+<ul>
+<li><a href='about.html'>About</a>
+<li><a href='docs.html'>Documentation</a>
+<li><a href='download.html'>Download</a>
+<li><a href='support.html'>Support</a>
+<li><a href='prosupport.html'>Purchase</a>
+</ul>
+</div>
+<div class="searchmenu" id="searchmenu">
+<form method="GET" action="search">
+<select name="s" id="searchtype">
+<option value="d">Search Documentation</option>
+<option value="c">Search Changelog</option>
+</select>
+<input type="text" name="q" id="searchbox" value="">
+<input type="submit" value="Go">
+</form>
+</div>
+</div>
+<script>
+function toggle_div(nm) {
+var w = document.getElementById(nm);
+if( w.style.display=="block" ){
+w.style.display = "none";
+}else{
+w.style.display = "block";
+}
+}
+function toggle_search() {
+var w = document.getElementById("searchmenu");
+if( w.style.display=="block" ){
+w.style.display = "none";
+} else {
+w.style.display = "block";
+setTimeout(function(){
+document.getElementById("searchbox").focus()
+}, 30);
+}
+}
+function div_off(nm){document.getElementById(nm).style.display="none";}
+window.onbeforeunload = function(e){div_off("submenu");}
+/* Disable the Search feature if we are not operating from CGI, since */
+/* Search is accomplished using CGI and will not work without it. */
+if( !location.origin || !location.origin.match || !location.origin.match(/http/) ){
+document.getElementById("search_menubutton").style.display = "none";
+}
+/* Used by the Hide/Show button beside syntax diagrams, to toggle the */
+function hideorshow(btn,obj){
+var x = document.getElementById(obj);
+var b = document.getElementById(btn);
+if( x.style.display!='none' ){
+x.style.display = 'none';
+b.innerHTML='show';
+}else{
+x.style.display = '';
+b.innerHTML='hide';
+}
+return false;
+}
+var antiRobot = 0;
+function antiRobotGo(){
+if( antiRobot!=3 ) return;
+antiRobot = 7;
+var j = document.getElementById("mtimelink");
+if(j && j.hasAttribute("data-href")) j.href=j.getAttribute("data-href");
+}
+function antiRobotDefense(){
+document.body.onmousedown=function(){
+antiRobot |= 2;
+antiRobotGo();
+document.body.onmousedown=null;
+}
+document.body.onmousemove=function(){
+antiRobot |= 2;
+antiRobotGo();
+document.body.onmousemove=null;
+}
+setTimeout(function(){
+antiRobot |= 1;
+antiRobotGo();
+}, 100)
+antiRobotGo();
+}
+antiRobotDefense();
+</script>
+
+
+<h1 align="center">Rowid Tables</h1>
+
+<h2>1.0 Definition</h2>
+
+<p>A "rowid table" is any table in an SQLite schema that
+<ul>
+<li>is <em>not</em> a <a href="vtab.html">virtual table</a>, and
+<li>is <em>not</em> a <a href="withoutrowid.html">WITHOUT ROWID</a> table.
+</ul>
+Most tables in a typical SQLite database schema are rowid tables.
+
+<p>Rowid tables are distinguished by the fact that they all have
+a unique, non-NULL, signed 64-bit integer <a href="lang_createtable.html#rowid">rowid</a> that is used as
+the access key for the data in the underlying <a href="fileformat2.html#btree">B-tree</a> storage engine.
+
+<h2>2.0 Quirks</h2>
+
+<ul>
+<li><p>
+The <a href="lang_createtable.html#primkeyconst">PRIMARY KEY</a> of a rowid table (if there is one) is usually not the
+true primary key for the table, in the sense that it is not the unique
+key used by the underlying <a href="fileformat2.html#btree">B-tree</a> storage engine. The exception to
+this rule is when the rowid table declares an <a href="lang_createtable.html#rowid">INTEGER PRIMARY KEY</a>.
+In the exception, the INTEGER PRIMARY KEY becomes an alias for the
+<a href="lang_createtable.html#rowid">rowid</a>.
+
+<li><p>
+The true primary key for a rowid table (the value that is used as the
+key to look up rows in the underlying <a href="fileformat2.html#btree">B-tree</a> storage engine)
+is the <a href="lang_createtable.html#rowid">rowid</a>.
+
+<li><p>
+The PRIMARY KEY constraint for a rowid table (as long as it is not
+the true primary key or INTEGER PRIMARY KEY) is really the same thing
+as a <a href="lang_createtable.html#uniqueconst">UNIQUE constraint</a>. Because it is not a true primary key,
+columns of the PRIMARY KEY are allowed to be NULL, in violation of
+all SQL standards.
+
+<li><p>
+The <a href="lang_createtable.html#rowid">rowid</a> of a rowid table can be accessed (or changed) by reading or
+writing to any of the "rowid" or "oid" or "_rowid_" columns. Except,
+if there is a declared columns in the table that use those
+special names, then those names refer to the declared columns, not to
+the underlying <a href="lang_createtable.html#rowid">rowid</a>.
+
+<li><p>
+Access to records via <a href="lang_createtable.html#rowid">rowid</a> is highly optimized and very fast.
+
+<li><p>
+If the <a href="lang_createtable.html#rowid">rowid</a> is not aliased by <a href="lang_createtable.html#rowid">INTEGER PRIMARY KEY</a> then it is not
+persistent and might change. In particular the <a href="lang_vacuum.html">VACUUM</a> command will
+change rowids for tables that do not declare an INTEGER PRIMARY KEY.
+Therefore, applications should not normally access the rowid directly,
+but instead use an INTEGER PRIMARY KEY.
+
+<li><p>
+In the underlying <a href="fileformat2.html">file format</a>, each rowid is stored as a
+<a href="fileformat2.html#varint">variable-length integer</a>. That means that small non-negative
+rowid values take up less disk space than large or negative
+rowid values.
+
+<li><p>
+All of the complications above (and others not mentioned here)
+arise from the need to preserve backwards
+compatibility for the hundreds of billions of SQLite database files in
+circulation. In a perfect world, there would be no such thing as a "rowid"
+and all tables would following the standard semantics implemented as
+<a href="withoutrowid.html">WITHOUT ROWID</a> tables, only without the extra "WITHOUT ROWID" keywords.
+Unfortunately, life is messy. The designer of SQLite offers his
+sincere apology for the current mess.
+</ul>
+<p align="center"><small><i>This page last modified on <a href="https://sqlite.org/docsrc/honeypot" id="mtimelink" data-href="https://sqlite.org/docsrc/finfo/pages/rowidtable.in?m=d768bc62edee4f842">2018-04-12 15:31:42</a> UTC </small></i></p>
+
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-23 08:22:19 +0000