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<title>Chapter 4. Using Cursors</title>
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<p>Library Version 11.2.5.3</p>
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<div>
<h2 class="title"><a id="Cursors"></a>Chapter 4. Using Cursors</h2>
</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>
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<dd>
<dl>
<dt>
<span class="sect2">
<a href="Positioning.html#cursorsearch">Searching for Records</a>
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<dt>
<span class="sect2">
<a href="Positioning.html#getdups">Working with Duplicate Records</a>
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</dd>
<dt>
<span class="sect1">
<a href="PutEntryWCursor.html">Putting Records Using Cursors</a>
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<dt>
<span class="sect1">
<a href="DeleteEntryWCursor.html">Deleting Records Using Cursors</a>
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<span class="sect1">
<a href="ReplacingEntryWCursor.html">Replacing Records Using Cursors</a>
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<a href="CoreCursorUsage.html">Cursor Example</a>
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<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>
<p>
Cursors are managed using the
<span><code class="classname">DBC</code> structure.</span>
To use a cursor, you must open it using the
<code class="methodname">DB->cursor()</code>
method.
</p>
<p>For example:</p>
<a id="c_cursor1"></a>
<pre class="programlisting">#include <db.h>
...
DB *my_database;
DBC *cursorp;
/* Database open omitted for clarity */
/* Get a cursor */
my_database->cursor(my_database, NULL, &cursorp, 0); </pre>
<p>
When you are done with the cursor, you should close it. To close a
cursor, call the
<code class="methodname">DBC->close()</code>
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.
It is recommended that you
close all cursor handles after their use to ensure concurrency and to release resources such as page locks.
</p>
<a id="c_cursor2"></a>
<pre class="programlisting">#include <db.h>
...
DB *my_database;
DBC *cursorp;
/* Database and cursor open omitted for clarity */
if (cursorp != NULL)
cursorp->close(cursorp);
if (my_database != NULL)
my_database->close(my_database, 0); </pre>
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