1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <title>Retrieving records</title> 7 <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" /> 10 <link rel="up" href="am.html" title="Chapter��3.�� Access Method Operations" /> 11 <link rel="prev" href="am_partition.html" title="Partitioning databases" /> 12 <link rel="next" href="am_put.html" title="Storing records" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Retrieving records</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="am_partition.html">Prev</a>��</td> 22 <th width="60%" align="center">Chapter��3.�� 23 Access Method Operations 24 </th> 25 <td width="20%" align="right">��<a accesskey="n" href="am_put.html">Next</a></td> 26 </tr> 27 </table> 28 <hr /> 29 </div> 30 <div class="sect1" lang="en" xml:lang="en"> 31 <div class="titlepage"> 32 <div> 33 <div> 34 <h2 class="title" style="clear: both"><a id="am_get"></a>Retrieving records</h2> 35 </div> 36 </div> 37 </div> 38 <p>The <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> method retrieves records from the database. In general, 39<a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> takes a key and returns the associated data from the 40database.</p> 41 <p>There are a few flags that you can set to customize retrieval:</p> 42 <div class="variablelist"> 43 <dl> 44 <dt> 45 <span class="term"> 46 <a href="../api_reference/C/dbget.html#get_DB_GET_BOTH" class="olink">DB_GET_BOTH</a> 47 </span> 48 </dt> 49 <dd>Search for a matching key and data item, that is, only return success 50if both the key and the data items match those stored in the database.</dd> 51 <dt> 52 <span class="term"> 53 <a href="../api_reference/C/dbcget.html#dbcget_DB_RMW" class="olink">DB_RMW</a> 54 </span> 55 </dt> 56 <dd>Read-modify-write: acquire write locks instead of read locks during 57retrieval. This can enhance performance in threaded applications by 58reducing the chance of deadlock.</dd> 59 <dt> 60 <span class="term"> 61 <a href="../api_reference/C/dbget.html#dbget_DB_SET_RECNO" class="olink">DB_SET_RECNO</a> 62 </span> 63 </dt> 64 <dd>If the underlying database is a Btree, and was configured so that it 65is possible to search it by logical record number, retrieve a specific 66record.</dd> 67 </dl> 68 </div> 69 <p>If the database has been configured to support duplicate records, 70<a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> will always return the first data item in the duplicate 71set.</p> 72 </div> 73 <div class="navfooter"> 74 <hr /> 75 <table width="100%" summary="Navigation footer"> 76 <tr> 77 <td width="40%" align="left"><a accesskey="p" href="am_partition.html">Prev</a>��</td> 78 <td width="20%" align="center"> 79 <a accesskey="u" href="am.html">Up</a> 80 </td> 81 <td width="40%" align="right">��<a accesskey="n" href="am_put.html">Next</a></td> 82 </tr> 83 <tr> 84 <td width="40%" align="left" valign="top">Partitioning databases��</td> 85 <td width="20%" align="center"> 86 <a accesskey="h" href="index.html">Home</a> 87 </td> 88 <td width="40%" align="right" valign="top">��Storing records</td> 89 </tr> 90 </table> 91 </div> 92 </body> 93</html> 94