my $inventoryInsert=...;
my $inventoryUpdate=...;
my $statement=...;
warn $inventoryUpdate.$statement."\n";
eval{
  $db->do($inventoryUpdate.$statement);
};
if ($@){
  warn "Can't update.  Trying insert.\n\n$inventoryInsert$statement";
  eval{
    $db->do($inventoryInsert.$statement);
  };
  if ($@){
    warn "Aborted because $@";
    $db->rollback;
    return 0;
  }
}
$db->commit;

##</code><code>##

Cannot insert the value NULL into column 'columnname', table 'tablename'; column does not allow nulls. UPDATE fails.

##</code><code>##

eval{
  $db->do($inventoryInsert.$statement);
#  $db->do($inventoryUpdate.$statement);
};
if ($@){
  warn "Can't update.  Trying insert.\n\n$inventoryInsert$statement";
  eval{
    $db->do($inventoryInsert.$statement);
  };
  if ($@){
    warn "Aborted because $@";
    $db->rollback;
    return 0;
  }
}
$db->commit;