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<h2 class="title" style="clear: both"><a id="readSecondary"></a>Reading Secondary Databases</h2>
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<p>
Like a primary database, you can read records from your secondary
database either by using the
<span>
<tt class="methodname">DB->get()</tt>
or
<tt class="methodname">DB->pget()</tt>
methods,
</span>
or by using
<span>a cursor on the secondary database.</span>
The main difference between reading secondary and primary databases is that when
you read a secondary database record, the secondary record's data is not
returned to you. Instead, the primary key and data corresponding to the
secondary key are returned to you.
</p>
<p>
For example, assuming your secondary database contains keys related
to a person's full name:
</p>
<a id="c_index6"></a>
<pre class="programlisting">#include <db.h>
#include <string.h>
...
DB *my_secondary_database;
DBT key; /* Used for the search key */
DBT pkey, pdata; /* Used to return the primary key and data */
char *search_name = "John Doe";
/* Primary and secondary database opens omitted for brevity */
/* Zero out the DBTs before using them. */
memset(&key, 0, sizeof(DBT));
memset(&pkey, 0, sizeof(DBT));
memset(&pdata, 0, sizeof(DBT));
key.data = search_name;
key.size = strlen(search_name) + 1;
/* Returns the key from the secondary database, and the data from the
* associated primary database entry.
*/
my_secondary_database->get(my_secondary_database, NULL,
&key, &pdata, 0);
/* Returns the key from the secondary database, and the key and data
* from the associated primary database entry.
*/
my_secondary_database->pget(my_secondary_database, NULL,
&key, &pkey, &pdata, 0); </pre>
<p>
Note that, just like
<span>a primary database,</span>
if your secondary database supports duplicate records then
<span>
<tt class="methodname">DB->get()</tt>
and
<tt class="methodname">DB->pget()</tt>
</span>
only return the first record found in a matching duplicates set. If you
want to see all the records related to a specific secondary key, then use a
<span>
cursor opened on the secondary database. Cursors are described in
<a href="Cursors.html">Using Cursors</a>.
</span>
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