title: Oracle Apex - Date effective non-overlapping dates via validation and interactive grid
body: <p>I'm trying to create a validation on create and update of an interactive editable grid in Oracle Apex 5.1. I right click the <code>effective_start_date</code> column and then choose Create Validation. From here I then set Type to Rows Returned with the idea of doing a select where there are other rows for the same date range as the current row being created or updated.</p>
  <p>To test I just entered <code>select 1 from dual</code> which I was thinking would then always error, but when I make changes I never get an error. Where am I going wrong and is this even possible in this manner?</p>