https://community.appian.com/support/w/kb/467/kb-1253-null-values-are-stored-as-empty-strings-when-writing-cdt-fields-to-a-databaseen-USTelligent Community 12https://community.appian.com/support/w/kb/467/kb-1253-null-values-are-stored-as-empty-strings-when-writing-cdt-fields-to-a-databaseTue, 07 Mar 2017 14:42:19 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:e2ac5dbf-0a8b-41d0-a7b0-10b75b391853Nick Vigilantehttps://community.appian.com/support/w/kb/467/kb-1253-null-values-are-stored-as-empty-strings-when-writing-cdt-fields-to-a-database#commentsCurrent Revision posted to Appian Knowledge Base by Nick Vigilante on 3/7/2017 2:42:19 PM<br /> <div class="row content_container"> <h2 id="symptoms">Symptoms</h2> <p>When saving the values of a CDT to a database, a NULL value is not stored as NULL - instead, it is stored as an empty string &lsquo;&rsquo;.</p> <h2 id="cause">Cause</h2> <p>Appian converts any NULL values of a CDT text field into an empty string. Writing an empty string to the database is safer than writing NULL value; a NULL value if not handled correctly can lead to NULL pointer exceptions.</p> <h2 id="workaround">Workaround</h2> <p>When comparing values returned from a data store, use <code>lenb()</code> to check the length in bytes is 0 which would be the equivalent of a NULL value. More information on the <code>lenb()</code> function can be found <a href="https://docs.appian.com/suite/help/latest/Text_Functions.html#lenb.28.29">here</a>.</p> <h2 id="affected-versions">Affected Versions</h2> <p>This article applies to all versions of Appian.</p> </div> <p>Last Reviewed:&nbsp;March 2017</p> <div style="clear:both;"></div> <div style="font-size: 90%;">Tags: CDTs, database, application design</div>