180 lines
5.8 KiB
HTML
180 lines
5.8 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
||
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
||
<html xmlns="http://www.w3.org/1999/xhtml">
|
||
<head>
|
||
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
|
||
<title>Chapter 4. Using Cursors</title>
|
||
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
||
<meta name="generator" content="DocBook XSL Stylesheets V1.62.4" />
|
||
<link rel="home" href="index.html" title="Getting Started with Berkeley DB" />
|
||
<link rel="up" href="index.html" title="Getting Started with Berkeley DB" />
|
||
<link rel="previous" href="DbCXXUsage.html" title="Database Usage Example" />
|
||
<link rel="next" href="Positioning.html" title="Getting Records Using the Cursor" />
|
||
</head>
|
||
<body>
|
||
<div class="navheader">
|
||
<table width="100%" summary="Navigation header">
|
||
<tr>
|
||
<th colspan="3" align="center">Chapter 4. Using Cursors</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="DbCXXUsage.html">Prev</a> </td>
|
||
<th width="60%" align="center"> </th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="Positioning.html">Next</a></td>
|
||
</tr>
|
||
</table>
|
||
<hr />
|
||
</div>
|
||
<div class="chapter" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h2 class="title"><a id="Cursors"></a>Chapter 4. Using Cursors</h2>
|
||
</div>
|
||
</div>
|
||
<div></div>
|
||
</div>
|
||
<div class="toc">
|
||
<p>
|
||
<b>Table of Contents</b>
|
||
</p>
|
||
<dl>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="Cursors.html#openCursor">Opening and Closing Cursors</a>
|
||
</span>
|
||
</dt>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="Positioning.html">Getting Records Using the Cursor</a>
|
||
</span>
|
||
</dt>
|
||
<dd>
|
||
<dl>
|
||
<dt>
|
||
<span class="sect2">
|
||
<a href="Positioning.html#cursorsearch">Searching for Records</a>
|
||
</span>
|
||
</dt>
|
||
<dt>
|
||
<span class="sect2">
|
||
<a href="Positioning.html#getdups">Working with Duplicate Records</a>
|
||
</span>
|
||
</dt>
|
||
</dl>
|
||
</dd>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="PutEntryWCursor.html">Putting Records Using Cursors</a>
|
||
</span>
|
||
</dt>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="DeleteEntryWCursor.html">Deleting Records Using Cursors</a>
|
||
</span>
|
||
</dt>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="ReplacingEntryWCursor.html">Replacing Records Using Cursors</a>
|
||
</span>
|
||
</dt>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="CoreCursorUsage.html">Cursor Example</a>
|
||
</span>
|
||
</dt>
|
||
</dl>
|
||
</div>
|
||
<p>
|
||
Cursors provide a mechanism by which you can iterate over the records in a
|
||
database. Using cursors, you can get, put, and delete database records. If
|
||
a database allows duplicate records, then cursors are
|
||
|
||
|
||
|
||
<span>the easiest way that you can access anything
|
||
other than the first record for a given key.</span>
|
||
</p>
|
||
<p>
|
||
This chapter introduces cursors. It explains how to open and close them, how
|
||
to use them to modify databases, and how to use them with duplicate records.
|
||
</p>
|
||
<div class="sect1" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h2 class="title" style="clear: both"><a id="openCursor"></a>Opening and Closing Cursors</h2>
|
||
</div>
|
||
</div>
|
||
<div></div>
|
||
</div>
|
||
<p>
|
||
Cursors are managed using the
|
||
|
||
<span><tt class="classname">Dbc</tt> class.</span>
|
||
To use a cursor, you must open it using the
|
||
|
||
<tt class="methodname">Db::cursor()</tt>
|
||
method.
|
||
</p>
|
||
<p>For example:</p>
|
||
<a id="cxx_cursor1"></a>
|
||
<pre class="programlisting">#include <db_cxx.h>
|
||
|
||
...
|
||
|
||
Dbc *cursorp;
|
||
Db my_database(NULL, 0);
|
||
|
||
// Database open omitted for clarity
|
||
|
||
// Get a cursor
|
||
my_database.cursor(NULL, &cursorp, 0); </pre>
|
||
<p>
|
||
When you are done with the cursor, you should close it. To close a
|
||
cursor, call the
|
||
|
||
<tt class="methodname">Dbc::close()</tt>
|
||
method. Note that closing your database while cursors are still opened
|
||
within the scope of the DB handle, especially if those cursors are
|
||
writing to the database, can have unpredictable results. Always
|
||
close your cursors before closing your database.
|
||
</p>
|
||
<a id="cxx_cursor2"></a>
|
||
<pre class="programlisting">#include <db_cxx.h>
|
||
|
||
...
|
||
|
||
Dbc *cursorp;
|
||
Db my_database(NULL, 0);
|
||
|
||
// Database and cursor open omitted for clarity
|
||
|
||
if (cursorp != NULL)
|
||
cursorp->close();
|
||
|
||
my_database.close(0);</pre>
|
||
</div>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="DbCXXUsage.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="index.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="Positioning.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">Database Usage Example </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> Getting Records Using the Cursor</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|