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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-13 14:07:11 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-13 14:07:11 +0000 |
commit | 63847496f14c813a5d80efd5b7de0f1294ffe1e3 (patch) | |
tree | 01c7571c7c762ceee70638549a99834fdd7c411b /www/c3ref/stmt_readonly.html | |
parent | Initial commit. (diff) | |
download | sqlite3-63847496f14c813a5d80efd5b7de0f1294ffe1e3.tar.xz sqlite3-63847496f14c813a5d80efd5b7de0f1294ffe1e3.zip |
Adding upstream version 3.45.1.upstream/3.45.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'www/c3ref/stmt_readonly.html')
-rw-r--r-- | www/c3ref/stmt_readonly.html | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/www/c3ref/stmt_readonly.html b/www/c3ref/stmt_readonly.html new file mode 100644 index 0000000..e71979a --- /dev/null +++ b/www/c3ref/stmt_readonly.html @@ -0,0 +1,173 @@ +<!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>Determine If An SQL Statement Writes The Database</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> +<!-- keywords: sqlite3_stmt_readonly --> +<div class=nosearch> +<a href="../c3ref/intro.html"><h2>SQLite C Interface</h2></a> +<h2>Determine If An SQL Statement Writes The Database</h2> +</div> +<blockquote><pre> +int sqlite3_stmt_readonly(sqlite3_stmt *pStmt); +</pre></blockquote> +<p> +The sqlite3_stmt_readonly(X) interface returns true (non-zero) if +and only if the <a href="../c3ref/stmt.html">prepared statement</a> X makes no direct changes to +the content of the database file.</p> + +<p>Note that <a href="../appfunc.html">application-defined SQL functions</a> or +<a href="../vtab.html">virtual tables</a> might change the database indirectly as a side effect. +For example, if an application defines a function "eval()" that +calls <a href="../c3ref/exec.html">sqlite3_exec()</a>, then the following SQL statement would +change the database file through side-effects:</p> + +<p><blockquote><pre> +SELECT eval('DELETE FROM t1') FROM t2; +</pre></blockquote></p> + +<p>But because the <a href="../lang_select.html">SELECT</a> statement does not change the database file +directly, sqlite3_stmt_readonly() would still return true.</p> + +<p>Transaction control statements such as <a href="../lang_transaction.html">BEGIN</a>, <a href="../lang_transaction.html">COMMIT</a>, <a href="../lang_transaction.html">ROLLBACK</a>, +<a href="../lang_savepoint.html">SAVEPOINT</a>, and <a href="../lang_savepoint.html">RELEASE</a> cause sqlite3_stmt_readonly() to return true, +since the statements themselves do not actually modify the database but +rather they control the timing of when other statements modify the +database. The <a href="../lang_attach.html">ATTACH</a> and <a href="../lang_detach.html">DETACH</a> statements also cause +sqlite3_stmt_readonly() to return true since, while those statements +change the configuration of a database connection, they do not make +changes to the content of the database files on disk. +The sqlite3_stmt_readonly() interface returns true for <a href="../lang_transaction.html">BEGIN</a> since +<a href="../lang_transaction.html">BEGIN</a> merely sets internal flags, but the <a href="../lang_transaction.html">BEGIN IMMEDIATE</a> and +<a href="../lang_transaction.html">BEGIN EXCLUSIVE</a> commands do touch the database and so +sqlite3_stmt_readonly() returns false for those commands.</p> + +<p>This routine returns false if there is any possibility that the +statement might change the database file. A false return does +not guarantee that the statement will change the database file. +For example, an UPDATE statement might have a WHERE clause that +makes it a no-op, but the sqlite3_stmt_readonly() result would still +be false. Similarly, a CREATE TABLE IF NOT EXISTS statement is a +read-only no-op if the table already exists, but +sqlite3_stmt_readonly() still returns false for such a statement.</p> + +<p>If prepared statement X is an <a href="../lang_explain.html">EXPLAIN</a> or <a href="../eqp.html">EXPLAIN QUERY PLAN</a> +statement, then sqlite3_stmt_readonly(X) returns the same value as +if the EXPLAIN or EXPLAIN QUERY PLAN prefix were omitted. +</p><p>See also lists of + <a href="../c3ref/objlist.html">Objects</a>, + <a href="../c3ref/constlist.html">Constants</a>, and + <a href="../c3ref/funclist.html">Functions</a>.</p> + |