Question

I have a fairly complex Oracle query, getting data from multiple tables. In one of the joins, I want the best record, if there is one. Therefore, a left outer join. There is a start date field, so for most records, getting the max start date will get me the best record. However, occasionally there are records that have the same start date. In that case, there is also a status field. However, the best status value is not a min or a max. ’20’ is best, ’05’ or ’40’ are ok, and ’70’ is worst. How can I set up the query to find the best option when multiple records are returned?

So, if I have the following data

Table1                       Table2
ID     otherData             ID      date      status    otherData
1      stuffa                1       jan-1-13  20        stuff93
2      stuff3                
3      stuff398              3       jan-2-13  20        stuff92
                             3       jan-2-13  70        stuff38
                             3       dec-3-12  20        stuff843

I will be able to query and get the following:

1   stuffa    jan-1-13  20  stuff93
2   stuff3
3   stuff398  jan-2-13  20  stuff92

Right now, my query is as follows, which gets a second record 3 with the 70 status:

select *
from table1 t1
left outer join
   (select *
    from table2 t2a
    where t2a.date = (select max(t2b.date)
                        from table2 t2b
                       where t2b.id = t2a.id)
    ) t2
  on (t2.id = t1.id)

Is there a way to set an ordered enumeration or something like that within a select statement? Something like

rank() over ( partition by status order by ('20','05','40','70') rank

Answer 1

add the status to the order by like this;

select *
  from (select t1.id,  t1.otherdata otherdatat1, t2.date, t2.status, t2.otherdata otherdatat2,
               rank() over (partition by t1.id order by t2.date desc,
                            case t2.status
                              when '20' then 1
                              when '05' then 2
                              when '40' then 3
                              when '70' then 4
                              else 5
                            end) rnk
          from table1 t1
               left outer join table2 t2
                            on t1.id = t2.id)
 where rnk = 1;