while ($data = $sth->fetchrow_array()) {
	$hash{$data} = undef;
}

##</code><code>##

$sql = 'SELECT col_1 FROM theTable';
.....
while ($data = $sty->fetchrow_array()) {
	push @my_list, $data;
}

##</code><code>##

$sql = 'SELECT col_1, col_2, col_3, col_4, col_5 FROM theTable';
.....
while (@data = $sty->fetchrow_array()) {
	$my_hash{$data[0]} = [ $data[1], $data[2], $data[3], $data[4] ];
}