Max qurey-view

Question

Hi eveybody:
I need your help. I have a table which primary key containes three fields. I would like to able to create a view select the maximum value of each key.
Primay Key Fields: PRIM_SEQ, START_DATE and END_DATE
Example:
PRIM_SEQ START_DATE END_DATE AMT_REQN
214 12/31/1999 12/31/1999 394775
214     1/1/2000 12/31/2000 0
214     1/1/2001 12/31/2001 50203
309 1/1/2002 12/31/2002 12548
309 1/1/2001 12/31/2001 858
309 1/1/2000 12/31/2000 0
309 1/1/1999 12/31/1999 589
309 2/1/2003 12/31/2003 788
309 1/1/2003 1/31/2003 11547
I would like my view only shows the followings records:
PRIM_SEQ START_DATE END_DATE AMT_REQN
214     1/1/2001 12/31/2001 50203
309 2/1/2003 12/31/2003 11547
Thanks,

Answer 1

Actually is probably neither 12548 nor 11547.
PK=(PRIM_SEQ, START_DATE, END_DATE) … but there likely is one important item that was left out: within each PRIM_SEQ partition, those [START_DATE, END_DATE] date ranges are mutually exclusive. It is kind of important for the MAX(START_DATE) and MAX(END_DATE) to be found on the same row within each partition.
SQL> alter session set nls_date_format='dd-mon-yyyy';
 
Session altered.
 
SQL> select * from ff order by 1,3;
 
  PRIM_SEQ START_DATE  END_DATE      AMT_REQN
       214 31-dec-1999 31-dec-1999     394775
       214 01-jan-2000 31-dec-2000          0
       214 01-jan-2001 31-dec-2001      50203
       309 01-jan-1999 31-dec-1999        589
       309 01-jan-2000 31-dec-2000          0
       309 01-jan-2001 31-dec-2001        858
       309 01-jan-2002 31-dec-2002      12548
       309 01-jan-2003 31-jan-2003      11547
       309 01-feb-2003 31-dec-2003        788
 
9 rows selected.
 
SQL> select ff.*
  2  from  ff
  3       ,( select prim_seq
  4                ,max(start_date) max_start_date
  5                ,max(end_date)   max_end_date
  6          from  ff
  7          group by prim_seq
  8        ) agg
  9  where  ff.prim_seq   = agg.prim_seq
10  and    ff.start_date = agg.max_start_date
11  and    ff.end_date   = agg.max_end_date
12  ;
 
  PRIM_SEQ START_DATE  END_DATE      AMT_REQN
       214 01-jan-2001 31-dec-2001      50203
       309 01-feb-2003 31-dec-2003        788
or with analytics …
SQL> select t.prim_seq
  2        ,t.start_date
  3        ,t.end_date
  4        ,t.amt_reqn
  5  from   ( select ff.*
  6                 ,case start_date
  7                     when max(start_date) over (partition by prim_seq) then 1
  8                     else 0
  9                  end last_ind
10           from  ff
11         ) t
12  where t.last_ind = 1
13  ;
 
  PRIM_SEQ START_DATE  END_DATE      AMT_REQN
       214 01-jan-2001 31-dec-2001      50203
       309 01-feb-2003 31-dec-2003        788That is my interpretation anyway.
One more thing ... an IOT will likely help here.