How can I count patterns of multiple rows in a table

Question

I just can't wrap my head around a query I need to identify the unique set of patterns with a table...by patterns I mean the following...
This is medical procedural data, wherein the first procedure code is followed by 0 or more procedures in a sequence for each case. I need to find out how many of each sequence of procedures exist in the table from all the cases...
row_id caseid proc_code sequence
1 1 A 1
2 1 B 2
3 2 C 1
4 3 A 1
5 3 B 2
So in this example data set I would like an output like this (something similar that would produce the number of times A followed B...and so on)
row_id proc_set count(*)
1 A-B 2
2 C 1
If someone could at least point me in a direction, I'd appreciate it...thanks ron.

Answer 1

Interesting variation, Solomon.Yes, but gives different results if there are more than two linked procedures:
SQL> with t as (
  2             select 1 case_id,'A' proc_code,1 seq from dual union all
  3             select 1,'B',2 from dual union all
  4             select 1,'C',3 from dual union all
  5             select 2,'C',1 from dual union all
  6             select 3,'A',1 from dual union all
  7             select 3,'B',2 from dual
  8            )
  9  select  proc_set,
10          count(*) cnt
11    from  (
12           select  case level
13                     when 1 then proc_code
14                     else connect_by_root(proc_code) || '-' || proc_cod
15                   end proc_set
16             from  t
17             where connect_by_isleaf = 1
18             start with seq = 1
19             connect by case_id = prior case_id
20                    and seq     = prior seq + 1
21          )
22    group by proc_set
23  /
PROC_SET                    CNT
A-B                           1
C                             1
A-C                           1While we get
SQL> with t as (
  2  select 1 row_id, 1 caseid, 'A' proc_code, 1 sequence from dual union
  3  select 2, 1, 'B', 2 from dual union
  4  select 4, 2, 'C', 1 from dual union
  5  select 3, 1, 'C', 3 from dual union
  6  select 5, 3, 'A', 1 from dual union
  7  select 6, 3, 'B', 2 from dual)
  8  select row_number() over (order by proc_set) row_id,  proc_set, count(0) from (
  9  select ltrim(sys_connect_by_path(proc_code,'-'),'-') proc_set
10    from t
11  where connect_by_isleaf=1
12  connect by prior sequence+1 = sequence and prior caseid=caseid
13  start with sequence=1)
14  group by proc_set;
    ROW_ID PROC_SET               COUNT(0)
         1 A-B                           1
         2 A-B-C                         1
         3 C                             1Max
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