Check and work out query based on continuity

Question

Hi all,
My Input:
1,2,3,4,7,8,9,11,12
I need to check the continuity and break to get output as
1-4,7-9,11-12
Can i get your help how to work out this?

Answer 1

SQL> with t
  2  as
  3  (
  4     select '1,2,3,4,7,8,9,11,12' str from dual
  5  ), no_tbl
  6  as
  7  (
  8     select to_number(substr(str,pos1, pos2-pos1)) no
  9       from (select str,instr(str,',',1,rno)+1 pos1, instr(str,',',1,rno+1) pos2
10               from (select rownum rno, ','||t.str||',' str
11                       from t, all_objects
12                      where rownum <= NVL( LENGTH( TRANSLATE(t.str, ',1234567890',',')), 0 )+1))
13  )
14  select min(no), max (no)
15    from (select no,
16            no - row_number() over (order by no) chg
17     from no_tbl)
18   group by chg
19   order by chg
20  /
   MIN(NO)    MAX(NO)
         1          4
         7          9
        11         12