Convert NOT IN to NOT EXISTS if possible

Question

Hi,
I have this query which is returning the correct results
SELECT hdr.order_num
               ,hdr.business_unit_id
               ,dtl.item_class_id
           FROM xxx.dd_ddhdr hdr
               ,xxx.dd_dddtl dtl
          WHERE hdr.order_num = dtl.order_num
            AND hdr.business_unit_id = dtl.business_unit_id
            AND dtl.item_class_id NOT IN
               SELECT cfl1.filtered_column_value
                 FROM sdds.ai_client_filter_list cfl1
                WHERE cfl1.client_id = 'XXT'
                  AND cfl1.filtered_column_name = 'ITEM_SUBCLASS'
                  AND cfl1.business_unit_id = hdr.business_unit_id
            AND hdr.order_datetime
            BETWEEN to_date('3/28/2007 13:21','mm/dd/yyyy hh24:mi:ss')
                AND to_date('3/28/2007 13:26','mm/dd/yyyy hh24:mi:ss');I converted the above query to use NOT EXISTS instead of NOT IN as follows:
SELECT hdr.order_num
               ,hdr.business_unit_id
               ,dtl.item_class_id
           FROM xxx.dd_ddhdr hdr
               ,xxx.dd_dddtl dtl
          WHERE hdr.order_num = dtl.order_num
            AND hdr.business_unit_id = dtl.business_unit_id
            -- AND dtl.item_class_id NOT IN
            AND NOT EXISTS
               select 1
                 from sdds.ai_client_filter_list cfl1
                where cfl1.client_id = 'XXT'
                  and cfl1.filtered_column_name = 'ITEM_SUBCLASS'
                  and hdr.business_unit_id = cfl1.business_unit_id
            AND hdr.order_datetime
            BETWEEN to_date('3/28/2007 13:21','mm/dd/yyyy hh24:mi:ss')
                AND to_date('3/28/2007 13:26','mm/dd/yyyy hh24:mi:ss');The 2nd query does not return any row after converting to NOT EXISTS.
Any idea to solve this?.
Thanks!

Answer 1

You can try this
SELECT hdr.order_num
               ,hdr.business_unit_id
               ,dtl.item_class_id
           FROM xxx.dd_ddhdr hdr
               ,xxx.dd_dddtl dtl
          WHERE hdr.order_num = dtl.order_num
            AND hdr.business_unit_id = dtl.business_unit_id
            AND NOT EXISTS
               SELECT noll
                 FROM sdds.ai_client_filter_list cfl1
                WHERE cfl1.client_id = 'XXT'
                  AND cfl1.filtered_column_name = 'ITEM_SUBCLASS'
                  AND cfl1.business_unit_id = hdr.business_unit_id
                  AND dtl.item_class_id = cfl1.filtered_column_value --<<--- you missed out this
            AND hdr.order_datetime
            BETWEEN to_date('3/28/2007 13:21','mm/dd/yyyy hh24:mi:ss')
                AND to_date('3/28/2007 13:26','mm/dd/yyyy hh24:mi:ss');Please keep in mind NOT IN and NOT EXISTS acts differently when it comes to NULL values
Check this out
select * from emp where empno not in (select mgr from emp)
select *
  from emp e
where not exists(select null from emp e1 where e.empno = e1.mgr)We expect the both to return the same result but they dont. Its because of the null value in the mgr column.
Now modify the NOT IN query like this and check
select * from emp where empno not in (select mgr from emp where mgr is not null) Edited by: Karthick_Arp on Sep 14, 2009 12:37 AM