$pagename = "something that tells me what si the name of the currnt script running, just its filename";

if ( $pagename is an already actual field inside table 'counter' then )
{
    $select = $db->prepare( "SELECT pagename, pagecounter FROM counters" );
    $select->execute;
}
else
{
    $select = $db->prepare( "INSERT INTO counters (pagename, pagecounter) VALUES (?, ?)" );
    $select->execute( $pagename, 1 );


my $pagecounter;
while( $row = $select->fetchrow_hashref )
{
    $pagecounter += $row->{pagecounter} unless ( $row->{host} eq "Νίκος" );
}