SQL joining question

Question

Here is my situation:

I have one table that contains a list of drugs sold containing the NDC (an identifier), quantity sold, and whether the drug is a brand name or

Answer 1

You can use a combination of Analytics (if you are on a recent enough version of Oracle) and a Pivot Table to do it. This should work with your dataset.

select ndc,
       max(decode(rn, 1, rx_num, null)) rx1,
       max(decode(rn, 2, rx_num, null)) rx2,
       max(decode(rn, 3, rx_num, null)) rx3,
       max(decode(rn, 4, rx_num, null)) rx4
  from (select *
          from (select claims_list.ndc,
                       claims_list.rx_num,
                       row_number() over (partition by claims_list.ndc order by claims_list.date desc) rn
                  from claims_list,
                       (select * 
                          from (select *
                                  from drug_list
                                 where type = 'Generic'
                                order by qty desc
                               )
                         where rownum < 51
                       ) drug_list
                 where drug_list.ndc = claims_list.ndc
               )
         where rn < 5
        order by ndc, rn
       )
group by ndc;

The inner query uses analytics to pull the most recent 4 rx numbers for each drug based on the claim date. Then we use a pivot to take it from 4 lines per drug to one line with 4 columns.