Does "OR" work here? Isn't it...
<?php if($WADAstats_details->getColumnVal("oppo45") || ($WADAstats_details->getColumnVal("oppoDate45")) || ($WADAstats_details->getColumnVal("venue45")) !== "") { ?>
Content you want to show here if all three columns have no value/data.
<?php } // Show if mysqli recordset empty ?>