sql query logic

Question

I have following data set

       a      b      c
      `1`     2      3
       3      6      9  
       9      2      11 

As you can see column a's first value is fixed (i.e. 1), but from second row it picks up the value of column c of previous record.

Column b's values are random and column c's value is calculated as c = a + b

I need to write a sql query which will select this data in above format. I tried writing using lag function but couldn't achieve.

Please help.

Edit : Column b exists in table only, a and c needs to calculated based on the values of b.

Hanumant

Answer 1

SQL> select a
  2       , b
  3       , c
  4    from dual
  5   model
  6         dimension by (0 i)
  7         measures (0 a, 0 b, 0 c)
  8         rules iterate (5)
  9         ( a[iteration_number] = nvl(c[iteration_number-1],1)
 10         , b[iteration_number] = ceil(dbms_random.value(0,10))
 11         , c[iteration_number] = a[iteration_number] + b[iteration_number]
 12         )
 13   order by i
 14  /

         A          B          C
---------- ---------- ----------
         1          4          5
         5          8         13
        13          8         21
        21          2         23
        23         10         33

5 rows selected.

Regards,
Rob.