$sth = $dbh->prepare(qq{select * from `table`});
$sth->execute();
my $_somevar = $sth->fetchrow_hashref();
$sth->finish();

##</code><code>##

$sth = $dbh->prepare(qq{select * from `table`});
$sth->execute();
while(my $_somevar = $sth->fetchrow_hashref()) {
my $_someid = $_somvar->{primarykeyfield};
$sth2 = $dbh->prepare(qq{select * from `table1` where `primarykeyfield` = ?});
$sth2->execute($_someid);
$_thisvar = $sth2->fetchrow_hashref();
$sth2->finish();
# now I have data from table in $_somvar
# and data from table1 in $_thisvar
}
$sth->finish();