mysql> select * from accounts limit 5 group by type;

SELECT account_type, account_balance FROM accounts WHERE account_type='savings'
   ORDER BY account_balance DESC LIMIT 5
UNION
SELECT account_type, account_balance FROM accounts WHERE account_type='chequing'
   ORDER BY account_balance DESC LIMIT 5
UNION
SELECT account_type, account_balance FROM accounts WHERE account_type='USD'
   ORDER BY account_balance DESC LIMIT 5;

SELECT *
FROM accounts a1
WHERE 5 >
(
   SELECT COUNT(*)
   FROM accounts a2
   WHERE a2.type = a1.type
   AND a2.balance > a1.balance
)

select * from accounts group by type limit 5;

SELECT a.*
FROM accounts a
     LEFT JOIN accounts a2 ON (a2.type = a.type AND a2.id < a.id)
WHERE count(a2.id) < 5
GROUP BY a.id;