Stuck on extracting row with smallest sequence_num

Question

I have this SQL from the po.po_action_history table in Oracle EBS:
SELECT pah.object_id
     , pah.object_sub_type_code
     , pah.sequence_num
     , pah.action_code
  FROM po.po_action_history pah
     , hr.per_all_people_f papf
     , po.po_requisition_headers_all prha
WHERE pah.object_id = prha.requisition_header_id
   AND pah.employee_id = papf.person_id
   AND SYSDATE BETWEEN papf.effective_start_date AND papf.effective_end_date
   AND pah.object_type_code = 'REQUISITION'
   AND pah.action_code = 'APPROVE'
   AND prha.segment1 = '5079536';
OBJECT_ID OBJECT_SUB_TYPE_CODE      SEQUENCE_NUM ACTION_CODE             
    851265 PURCHASE                             4 APPROVE                 
    851265 PURCHASE                             9 APPROVE                 
    851265 PURCHASE                             2 APPROVE                 
    851265 PURCHASE                             6 APPROVE                 
4 rows selected.I need to only return the row with the smallest SEQUENCE_NUM, but I can't work out how to do it.
If this was MySQL, I could just do:
SELECT pah.object_id
     , pah.object_sub_type_code
     , pah.sequence_num
     , pah.action_code
  FROM po.po_action_history pah
     , hr.per_all_people_f papf
     , po.po_requisition_headers_all prha
WHERE pah.object_id = prha.requisition_header_id
   AND pah.employee_id = papf.person_id
   AND SYSDATE BETWEEN papf.effective_start_date AND papf.effective_end_date
   AND pah.object_type_code = 'REQUISITION'
   AND pah.action_code = 'APPROVE'
   AND prha.segment1 = '5079536'
   ORDER BY sequence_num ASC LIMIT 1;But I know that's a waste of time as it isn't MySQL! But hopefully you can see my point. The above is just an example - I know I could just say "WHERE sequence_num= 2", but I have a whole load of transactions I need to analyse, and for each one I need to return the info from the po_action_history table for the earliest / first instance where the action_code = APPROVE.
Any advice much appreciated.
Thanks!

Answer 1

Hi ,
You can try to use the rank function to acheive the desired results.
As you have not posted the create/insert statements am using the with clause to populate the data
Try this code
WITH t AS
  SELECT '851265' AS OBJECT_ID,'PURCHASE' AS OBJECT_SUB_TYPE_CODE,'4' AS SEQUENCE_NUM,'APPROVE' AS ACTION_CODE
  FROM dual
  UNION ALL
  SELECT '851265','PURCHASE','9','APPROVE'
  FROM dual
  UNION ALL
  SELECT '851265','PURCHASE','2','APPROVE'
  FROM dual
  UNION ALL
  SELECT '851265','PURCHASE','6','APPROVE'
  FROM dual
  UNION ALL
  SELECT '851266','PURCHASE','6','APPROVE'
  FROM dual
  UNION ALL
  SELECT '851266','PURCHASE','4','APPROVE'
  FROM dual
  UNION ALL
  SELECT '851266','PURCHASE','8','APPROVE'
  FROM dual
  UNION ALL
  SELECT '851266','PURCHASE','5','APPROVE'
  FROM dual
  UNION ALL
  SELECT '851266','PURCHASE','3','APPROVE'
  FROM dual
SELECT object_id,object_sub_type_code,SEQUENCE_NUM
FROM (
SELECT object_id,object_sub_type_code,SEQUENCE_NUM,ACTION_CODE,rank() OVER (PARTITION BY OBJECT_ID ORDER BY SEQUENCE_NUM ) rn
FROM t)
where rn=1Modify your query like mentioned below
SELECT object_id,object_sub_type_code,SEQUENCE_NUM
FROM (
SELECT object_id,object_sub_type_code,SEQUENCE_NUM,ACTION_CODE,rank() OVER (PARTITION BY OBJECT_ID ORDER BY SEQUENCE_NUM ) rn
FROM t)
where rn=1Hope this helps.
Regards,
Achyut