$last_value='';
while ( $item = mysqli_fetch_array( $result ) ) {
$html. = '<tr>'."\r\n";
$html. = '<td>'.$item['a1'].'</td>'."\r\n";
$html. = '<td>'.$item['b1'].'</td>'."\r\n";
$html. = '</tr>'."\r\n";
if ($item['a1'] == $last_value) {
$html. = '<tr>'."\r\n";
$html. = '<td> </td>'."\r\n";
$html. = '<td> </td>'."\r\n";
$html. = '</tr>'."\r\n";
}
$last_value = $item['a1']; //можно добавить в else, но можно и так.
}
SUBSTRING(`utemp`.`CODEM`, 1, 3) = SUBSTRING(`u`.`CODEM`, 1, 3)