Please tell me the Query

Question

Hi,
I need the query, please give me the solution.
SQL> select rownum SNo,nvl(CAT,'NULL') Category, nvl(VAL,'NULL') Value from rownum_test;
SNO CATEGORY VALUE
1 Cat1 Mango
2 NULL Juice
3 NULL NULL
4 Cat2 Apple
5 NULL Apple Juice
Need the logic:
For CATEGORY if there is NULL value then it should pick up its previous value. and same for the VALUE field.
The output should be:
SNO CATEGORY VALUE
1 Cat1 Mango
2 Cat1 Juice
3 Cat1 Juice
4 Cat2 Apple
5 Cat2 Apple Juice
Thanks in advance
Amit Kumar

Answer 1

It depends on which version of oracle you are using...
SQL> select * from samp;
   ROW_NUM CAT  VAL
         1 CAT1 MANGO
         2      JUICE
         3
         4 CAT2 APPLE
         5      APPLE JUICE
SQL> In 10g, release 2 the query would be
SQL> select row_num,
  2  last_value(cat ignore nulls)
  3   over (order by row_num) cat,
  4  last_value(val ignore nulls)
  5   over (order by row_num) val
  6  from samp
  7  order by row_num;
   ROW_NUM CAT  VAL
         1 CAT1 MANGO
         2 CAT1 JUICE
         3 CAT1 JUICE
         4 CAT2 APPLE
         5 CAT2 APPLE JUICE
SQL> In Oracle 9i, the query would be
  1  select row_num,
  2   substr(max(case when cat is not null then
  3    to_char(row_num,'fm000')||cat end)
  4     over (order by row_num),4) cat,
  5   substr(max(case when val is not null then
  6    to_char(row_num,'fm000')||val end)
  7     over (order by row_num),4) val
  8  from samp
  9* order by row_num
SQL> /
   ROW_NUM CAT   VAL
         1 CAT1  MANGO
         2 CAT1  JUICE
         3 CAT1  JUICE
         4 CAT2  APPLE
         5 CAT2  APPLE JUICE
SQL> This was discussed by Thomas Kyte on Oracle magazine..