CREATE TABLE Table_a
(
  SEQ      NUMBER,
  INSTANCE  NUMBER
)
/

SET DEFINE OFF;
Insert into Table_a
   (SEQ, INSTANCE)
 Values
   (1, 4);
Insert into Table_a
   (SEQ, INSTANCE)
 Values
   (2, 274);
Insert into Table_a
   (SEQ, INSTANCE)
 Values
   (3, 18);
Insert into Table_a
   (SEQ, INSTANCE)
 Values
   (4, 26);
Insert into Table_a
   (SEQ, INSTANCE)
 Values
   (5, 14);
COMMIT;
/

CREATE TABLE Table_b
(
  E_DATE              DATE,
  ACC                 VARCHAR2(8)      NOT NULL,
  INSTANCE              NUMBER            NOT NULL,
  TOTAL_VALUE             NUMBER(38)
)
/

SET DEFINE OFF;
Insert into Table_b
   (INSTANCE, E_DATE, ACC, TOTAL_VALUE)
 Values
   (14, TO_DATE('11/30/2011 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), 'RR', 475.74);
Insert into Table_b
   (INSTANCE, E_DATE, ACC, TOTAL_VALUE)
 Values
   (18, TO_DATE('11/30/2011 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), 'RR', 479.99);
Insert into Table_b
   (INSTANCE, E_DATE, ACC, TOTAL_VALUE)
 Values
   (26, TO_DATE('11/30/2011 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), 'RR', 422.34);
COMMIT;
/

ACC				E_DATE			INSTANCE		TOTAL_VALUE
RR			30-Nov-2011			18				479.99

SQL> with 
  2    data as (
  3      select a.seq, a.instance, b.e_date, b.acc, b.total_value
  4      from table_a a, table_b b
  5      where b.instance = a.instance
  6      order by a.seq
  7    )
  8  select acc, e_date, instance, total_value
  9  from data
 10  where rownum = 1
 11  /
ACC      E_DATE                INSTANCE TOTAL_VALUE
-------- ------------------- ---------- -----------
RR       30/11/2011 00:00:00         18         480

1 row selected.