Ranking of Consecutive non-increasing values in a column

Question

Hi friends
I have a table with numbers like this in a column
sr no.        value
1               17
2                0
3                0
4              38
5              32
6              24
7              12
8              51
9              42
10              1
11              1
12              0
13              0
14              1
15              1
so on....I want to find out consecutive non-increasing sequences of value (2nd column) order by sr. no (first column) in ascending order.
For example, in the 2nd column, 17 is followed by 0 and 0 and then 38 so it means 3 consecutive values (i.e starting from 17 are 0 and 0) are non-increasing and they are ranked by '1' in my desired in third column as shown below. similarly, the 2nd non-increasing sequence starts with 38,32,24 and 12 and this is ranked as '2' in the third column. same is the case with rank '3' for the third non increasing sequence. so bascially i want the third column with "ranks" starting and ending as per above logic. i tried using LEAD function but doesn't get what I want. I need the shortest possible query to get that third column since i have other columns in the original table in a multiple group by query.
my desired output is:
sr no.        value              Rank
1               17                 1
2                0                  1
3                0                  1
4              38                  2
5              32                  2
6              24                  2
7              12                  2
8              51                  3
9              42                  3
10              1                  3
11              1                  3
12              0                  3
13              0                  3
14              1                  4
15              1                  4
.                  Hope I explained the question clearly and hoping to get answer soonest.
regards
Hamza

Answer 1

with sample_table as (
                      select 1 sr_no,17 val from dual union all
                      select 2,0 from dual union all
                      select 3,0 from dual union all
                      select 4,38 from dual union all
                      select 5,32 from dual union all
                      select 6,24 from dual union all
                      select 7,12 from dual union all
                      select 8,51 from dual union all
                      select 9,42 from dual union all
                      select 10,1 from dual union all
                      select 11,1 from dual union all
                      select 12,0 from dual union all
                      select 13,0 from dual union all
                      select 14,1 from dual union all
                      select 15,1 from dual
               t1 as (
                      select  sr_no,
                              val,
                              case
                                when lag(val) over(order by sr_no) >= val then 0
                                else 1
                              end start_of_group
                        from  sample_table
select  sr_no,
        val,
        sum(start_of_group) over(order by sr_no) rank
  from  t1
  order by sr_no
     SR_NO        VAL       RANK
         1         17          1
         2          0          1
         3          0          1
         4         38          2
         5         32          2
         6         24          2
         7         12          2
         8         51          3
         9         42          3
        10          1          3
        11          1          3
     SR_NO        VAL       RANK
        12          0          3
        13          0          3
        14          1          4
        15          1          4
15 rows selected.
SQL> SY.