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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Dynamically Typed Value Object</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="intro.html"><h2>SQLite C Interface</h2></a><h2>Dynamically Typed Value Object</h2><blockquote><pre>typedef struct Mem sqlite3_value;</pre></blockquote><p>SQLite uses the sqlite3_value object to represent all valuesthat can be stored in a database table.SQLite uses dynamic typing for the values it stores.Values stored in sqlite3_value objects can bebe integers, floating point values, strings, BLOBs, or NULL.</p><p>An sqlite3_value object may be either "protected" or "unprotected".Some interfaces require a protected sqlite3_value. Other interfaceswill accept either a protected or an unprotected sqlite3_value.Every interface that accepts sqlite3_value arguments specifieswhether or not it requires a protected sqlite3_value.</p><p>The terms "protected" and "unprotected" refer to whether or nota mutex is held. A internal mutex is held for a protectedsqlite3_value object but no mutex is held for an unprotectedsqlite3_value object. If SQLite is compiled to be single-threaded(with SQLITE_THREADSAFE=0 and with <a href="../c3ref/threadsafe.html">sqlite3_threadsafe()</a> returning 0)then there is no distinction betweenprotected and unprotected sqlite3_value objects and they can beused interchangable. However, for maximum code portability itis recommended that applications make the distinction betweenbetween protected and unprotected sqlite3_value objects even ifthey are single threaded.</p><p>The sqlite3_value objects that are passed as parameters into theimplementation of application-defined SQL functions are protected.The sqlite3_value object returned by<a href="../c3ref/column_blob.html">sqlite3_column_value()</a> is unprotected.Unprotected sqlite3_value objects may only be used with<a href="../c3ref/result_blob.html">sqlite3_result_value()</a> and <a href="../c3ref/bind_blob.html">sqlite3_bind_value()</a>. All otherinterfaces that use sqlite3_value require protected sqlite3_value objects.</p><p>See also lists of <a href="objlist.html">Objects</a>, <a href="constlist.html">Constants</a>, and <a href="funclist.html">Functions</a>.</p><hr><small><i>This page last modified 2008/02/21 17:46:11 UTC</i></small></div></body></html>⌨️ 快捷键说明
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