my $limit = 1;
my $query = qq{SELECT id FROM table ORDER BY RAND() LIMIT $limit};
my $ids = $dbh->selectcol_arrayref($query)
    or die "execution error ($DBI::errstr\n";
$query = qq{SELECT question, answer FROM table
    WHERE id in (}
    . (join ",", @$ids)
    . " ) " ;

##</code><code>##

mysql> create table if not exists support_tbl
    -> (cnt int not null auto_increment primary key,
    -> id int not null);
mysql> truncate support_tbl;
mysql> insert into support_tbl (id) select id from table order by rand();

##</code><code>##

my $cnt =1;
my $ids = $dbh->selectcol_arrayref(qq{select id from 
    support_tbl where cnt = ?}, undef, $cnt);

##</code><code>##

# make sure our random value is not higher than
# any value in the primary key
my ($max) = @{$dbh->selectcol_arrayref(qq{select max(id) from table})};
my $cnt = rand($max);
my $query = qq{SELECT question, answer FROM table WHERE id = $cnt };