Utilice la siguiente consulta:
SELECT E.I_EmpID AS EMPID,
E.I_EMPCODE AS EMPCODE,
E.I_EmpName AS EMPNAME,
REPLACE(TO_CHAR(A.I_REQDATE, 'DD-Mon-YYYY'), ' ', '') AS FROMDATE,
REPLACE(TO_CHAR(A.I_ENDDATE, 'DD-Mon-YYYY'), ' ', '') AS TODATE,
TO_CHAR(NOD) AS NOD,
DECODE(A.I_DURATION,
'FD',
'FullDay',
'FN',
'ForeNoon',
'AN',
'AfterNoon') AS DURATION,
L.I_LeaveType AS LEAVETYPE,
REPLACE(TO_CHAR((SELECT max(C.I_WORKDATE)
FROM T_COMPENSATION C
WHERE C.I_COMPENSATEDDATE = A.I_REQDATE
AND C.I_EMPID = A.I_EMPID),
'DD-Mon-YYYY'),
' ',
'') AS WORKDATE,
A.I_REASON AS REASON,
AP.I_REJECTREASON AS REJECTREASON
FROM T_LEAVEAPPLY A
INNER JOIN T_EMPLOYEE_MS E
ON A.I_EMPID = E.I_EmpID
AND UPPER(E.I_IsActive) = 'YES'
AND A.I_STATUS = '1'
INNER JOIN T_LeaveType_MS L
ON A.I_LEAVETYPEID = L.I_LEAVETYPEID
LEFT OUTER JOIN T_APPROVAL AP
ON A.I_REQDATE = AP.I_REQDATE
AND A.I_EMPID = AP.I_EMPID
AND AP.I_APPROVALSTATUS = '1'
WHERE E.I_EMPID <> '22'
ORDER BY A.I_REQDATE DESC
El truco consiste en forzar que la consulta interna devuelva solo un registro agregando una función agregada (he usado max() aquí). Esto funcionará perfectamente en lo que respecta a la consulta, pero, honestamente, OP debería investigar por qué la consulta interna devuelve múltiples registros al examinar los datos. ¿Estos registros múltiples son realmente relevantes desde el punto de vista empresarial?