Update does not doing updates

[sam wun]

Hi,

I use the following statement to update a table, but I don't see the 
testing record being updated:

 $udpate_sql = qq {update transaction
                             set salesvolume=$salesvol, 
netsales=$netsales, transtype="$transtype",
                                 returnreason="$returnreason"
                             where prodcode="$prodcode" and 
custcode="$custcode" and date="$transdate";};
$sth = $dbh->prepare($update_sql) || die "prepare: $update_sql: 
$DBI::errstr";
$sth->execute || die "Unable to execute query: $dbh->errstr\n";
$sth->finish;

Thanks
Sam