## Try using UNION ALL  in place of UNION (where possible)


   SELECT ACCT_NUM, BALANCE_AMT
   FROM   DEBIT_TRANSACTIONS
   WHERE  TRAN_DATE = ‘31-DEC-95’
   UNION
   SELECT ACCT_NUM, BALANCE_AMT
   FROM   CREDIT_TRANSACTIONS
   WHERE  TRAN_DATE = ‘31-DEC-95’


## To improve performance, replace this code with:

   SELECT ACCT_NUM, BALANCE_AMT
   FROM   DEBIT_TRANSACTIONS
   WHERE  TRAN_DATE = ‘31-DEC-95’
   UNION ALL
   SELECT ACCT_NUM, BALANCE_AMT
   FROM   CREDIT_TRANSACTIONS
   WHERE  TRAN_DATE = ‘31-DEC-95’