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<!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" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii" /> <meta http-equiv="Content-Style-Type" content="text/css" /> <meta http-equiv="Content-Script-Type" content="text/javascript" /> <title>Referencing a Null Value in an Item Based on an LOV</title> <meta name="generator" content="Oracle DARB XHTML Converter (Mode = ohj/ohw) - Version 5.1" /> <meta name="date" content="2009-04-14T16:11:29Z" /> <meta name="robots" content="noarchive" /> <meta name="doctitle" content="Referencing a Null Value in an Item Based on an LOV" /> <meta name="relnum" content="Release 3.2" /> <meta name="partnum" content="E11947-01" /> <link rel="copyright" href="dcommon/html/cpyr.htm" title="Copyright" type="text/html" /> <link rel="stylesheet" href="dcommon/css/blafdoc.css" title="Oracle BLAFDoc" type="text/css" /> <link rel="contents" href="toc.htm" title="Contents" type="text/html" /> <link rel="up" href="preface.htm" title="Home" type="text/html" /> <link rel="up" href="app_comp.htm" title="Adding Application Components" type="text/html" /> <link rel="up" href="bldapp_lov.htm" title="Creating Lists of Values" type="text/html" /> <link rel="up" href="bldapp_lov_null.htm" title="Referencing a Null Value in..." type="text/html" /> <link rel="prev" href="bldapp_lov_session.htm" title="Previous" type="text/html" /> <link rel="next" href="bldapp_lov_rpts.htm" title="Next" type="text/html" /> </head> <body> <p id="BREADCRUMBING"><a href="preface.htm" title="Home">Home</a> > <a href="app_comp.htm" title="Adding Application Components">Adding Application Components</a> > <a href="bldapp_lov.htm" title="Creating Lists of Values">Creating Lists of Values</a> > Referencing a Null Value in...</p> <table class="simple oac_no_warn" summary="" cellspacing="0" cellpadding="0" width="100%"> <col width="86%" /> <col width="*" /> <tr valign="bottom"> <td align="left"></td> <td align="center"><a href="bldapp_lov_session.htm"><img src="dcommon/gifs/leftnav.gif" alt="Previous" /><br /> <span class="icon">Previous</span></a> </td> <td align="center"><a href="bldapp_lov_rpts.htm"><img src="dcommon/gifs/rightnav.gif" alt="Next" /><br /> <span class="icon">Next</span></a></td> </tr> </table> <p><a id="CEGIBEDE" name="CEGIBEDE"></a></p> <div class="sect2"><!-- infolevel="all" infotype="General" --> <h1><a name="HTMDB25457" id="HTMDB25457"></a>Referencing a Null Value in an Item Based on an LOV<a id="sthref1220" name="sthref1220"></a></h1> <p>LOVs have a null display value option and a null return value option. The null display value is the value the end user sees in the list indicating the no selection from the proper (non-null) values of the list will be made. When a user selects a null display value, the LOV's null return value is sent to the application when the page is submitted. If the developer has left the null return value unspecified (or empty), the actual value transmitted is not an empty string or an Oracle null, but the literal <code>%null%</code>. The application must be prepared to deal with this literal and treat is as the null selection.</p> <p>Be aware of this behavior when writing code to evaluate submitted values. For example, suppose a page evaluates the submitted item <code>P1_X</code> and you need to use the PL/SQL expression <code>replace(:P1_X,'%'||'null%',null)</code> to prepare the item for permanent storage in session state or for passing to DML or other APIs.</p> <p>To avoid problems, be aware of the appropriate way to code <code>%null%</code> in expressions that occur in page computations, processes, and validations. You must break up the string so that the application does not replace <code>%null%</code> with a null value in the page metadata when it is saved. Consider the following example:</p> <pre xml:space="preserve" class="oac_no_warn"> '%'||'null%' </pre></div> <!-- class="sect2" --> <!-- Start Footer --> <div class="footer"> <table class="simple oac_no_warn" summary="" cellspacing="0" cellpadding="0" width="100%"> <col width="86%" /> <col width="*" /> <tr> <td align="left"><span class="copyrightlogo">Copyright © 2003, 2009, Oracle and/or its affiliates. All rights reserved.</span><br /> <a href="dcommon/html/cpyr.htm"><span class="copyrightlogo">Legal Notices</span></a></td> <td align="center"><a href="bldapp_lov_session.htm"><img src="dcommon/gifs/leftnav.gif" alt="Previous" /><br /> <span class="icon">Previous</span></a> </td> <td align="center"><a href="bldapp_lov_rpts.htm"><img src="dcommon/gifs/rightnav.gif" alt="Next" /><br /> <span class="icon">Next</span></a></td> </tr> </table> </div> <!-- class="footer" --> </body> </html>
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