Oracle Sql performance very slow

Question

I have created aquery that joins several tables in Oracle, but the execution time is very slow, around 1-2 minutes. Is there a method to make the query faster?

SELECT S.ID STAFF_ID,
        d.year_enrol,
        C.COUNSELLOR_ID,
        count(*) Num_Of_Stud
FROM aab_ASSIGNED_COUNSELLOR C,
     aab_STAFF S,
     v_aab_student d
WHERE C.COUNSELLOR_ID = S.COUNSELLOR_ID
  AND SYSDATE BETWEEN C.EFFECTIVE_DATE_FM AND C.EFFECTIVE_DATE_TO
  AND C.HOST_COUNSELLOR_IND = 'Y'
  AND c.student_num = d.student_num
  AND (d.prog_code, d.subcode) NOT IN (('11345',' '),
                                       ('22678',' '),
                                       ('93451', ' '),
                                       ('62378','OPT'))
GROUP BY S.ID,
         d.year_enrol,
         C.COUNSELLOR_ID;

Answer 1

You should create index for each variable involve in the where part. You could create simple index or a composite for with all the field.

Create Index for each fields on the WHERE not just the Primary Key

aab_ASSIGNED_COUNSELLOR

COUNSELLOR_ID 
EFFECTIVE_DATE_FM 
HOST_COUNSELLOR_IND 
student_num 

aab_STAFF

COUNSELLOR_ID

v_aab_student

student_num
prog_code
subcode

Also you can use Explain Plan to see what is doing the query. Sometime even when you add the index the planner decide not use it. That depend on your data size.

ADDED notes.

USE INNER JOIN instead of WHERE syntaxis, this wont improve performace just for better reading

And you may try creating an implicit table instead of using IN . With Left JOIN and T.prog_code IS NULL do the trick.

SELECT     s.id staff_id, d.year_enrol, c.counsellor_id, Count(*) num_of_stud 
FROM       aab_assigned_counsellor C 
INNER JOIN aab_staff S, 
        ON c.counsellor_id = s.counsellor_id 
INNER JOIN v_aab_student D 
        ON c.student_num = d.student_num 
LEFT JOIN 
           ( 
               SELECT '11345' prog_code,  ' '     subcode 
               UNION 
               SELECT '22678' prog_code,  ' '     subcode 
               UNION 
               SELECT '93451' prog_code,  ' '     subcode 
               UNION  
               SELECT '62378' prog_code,  'OPT'   subcode 
           ) AS T
       ON  D.prog_code = T.prog_code 
      AND  D.subcode = T.subcode 
WHERE      C.host_counsellor_ind = 'Y' 
AND        T.prog_code IS NULL 
AND        sysdate BETWEEN C.effective_date_fm AND C.effective_date_to 
GROUP BY   S.id, D.year_enrol, C.counsellor_id;