Originally posted by dharma
did you try using
AND (C1_REC.group_ofstudy IS NULL AND C3_REC.value IS NULL) to see if they are working.
Code:
TUNE: U_HRENG> r
  1  SELECT
  2  C1_REC.fk_employee_id EMPID_1,
  3  C2_REC.fk_employee_id EMPID_2,
  4  RPAD(C1_REC.fk_exam_level,25) EX_1,
  5  RPAD(C4_REC.value1,25) EX_2,
  6  RPAD(C1_REC.fk_qualification,25) QU_1,
  7  RPAD(C4_REC.value2,25) QU_2,
  8  RPAD(C1_REC.group_ofstudy,55) GRP_1,
  9  RPAD(C3_REC.value,55) GRP_2,
 10  RPAD(C1_REC.institution,55) INS_1,
 11  RPAD(C3_REC.value,55) INS_2,
 12  C1_REC.month_of_passing MON_1,
 13  C2_REC.month_of_passing MON_2,
 14  C1_REC.year_of_passing YR_1,
 15  C2_REC.year_of_passing YR_2,
 16  C1_REC.grade GR_1,
 17  C2_REC.grade GR_2
 18  FROM
 19  u_port.d_hris_academic C1_REC,
 20  d_sip_personal_academic C2_REC,
 21  d_sip_config_single C3_REC,
 22  d_sip_config_double C4_REC
 23  WHERE
 24  C1_REC.fk_employee_id = C2_REC.fk_employee_id
 25  AND C1_REC.fk_exam_level = C4_REC.value1
 26  AND C1_REC.fk_qualification = C4_REC.value2
 27  -- AND C4_REC.double_config_id = C2_REC.fk_qualif_double_config_id
 28  --AND (NVL(C1_REC.group_ofstudy,'*') = NVL(C3_REC.value,'*'))
 29  AND (C1_REC.group_ofstudy is null and C3_REC.value is null)
 30  AND C3_REC.single_config_id = C2_REC.fk_course_single_config_id
 31  AND C1_REC.institution = C3_REC.value
 32  AND C3_REC.single_config_id = C2_REC.fk_inst_single_config_id
 33  AND C1_REC.month_of_passing = C2_REC.month_of_passing
 34  AND C1_REC.year_of_passing = C2_REC.year_of_passing
 35  AND C1_REC.grade = C2_REC.grade
 36* ORDER BY 1,2

no rows selected

Originally posted by dharma
check if both fields are of same datatypes
Yea, both the fields are VARCHAR2.

Thanks for the effort.