Handling duplicates in a mysql database using php
<p>I am developing a Political Campaign scheduling system. I have a table called <code>schedule</code> with fields; <code>Date</code>, <code>candidate_id</code>, <code>campaign_center</code>, and <code>route</code>.</p>

<p>I do not want candidates to go in the same campaigning center and I want the candidates to never meet during the rallies. Therefore, they should never use the same route. I have made <code>Date</code>, <code>campaign_center</code>, and <code>route</code> fields primary keys. </p>

<p>I need help printing out an error message once different candidates are assigned  the same route or the same rally location. How do I code it?. Thanks</p>
