When I run that code, I get "there is an error in your SQL"
I have since changed the code to"
$UpdateQuery->bindColumn("batch_date", "t", "".($rsDecisions->getColumnVal("batch_date")?"":$_POST["batch_date"]) ."", "WA_IGNORE");
As the field to check is $rsDecisions->getColumnVal("batch_date"") rather than the rsBatch_dates one.
Now when I submit, it just goes to a blank page (without updating).