Recursive Hierarchical Query with CONNECT BY/START WITH

Question

I want to traverse a tree which has is not hierarchical in linear sense. You know, like :
A
B
C
D
E
C
F
D
E
C
You see that D, Eand C are repeated and C is under E as well as under B. I tried using CONNECT BY and START WITH but I get tripliate occurances of C under B, and 2 occurances of DEC under A and under F. Clearly this is not correct. I believe SQL3 has special way of handling with such recursive trees. How does O9i handle these constructs? Please help.

Answer 1

CREATE OR REPLACE PACKAGE hierarchy
IS
  TYPE branchtable_type IS TABLE OF VARCHAR2 (4000)
  INDEX BY BINARY_INTEGER;
  branchtable branchtable_type;
  FUNCTION branch
    (v_level     IN NUMBER,
     v_value     IN VARCHAR2,
     v_delimeter IN VARCHAR2 DEFAULT CHR (0))
    RETURN VARCHAR2;
  PRAGMA RESTRICT_REFERENCES (branch, WNDS);
END hierarchy;
CREATE OR REPLACE PACKAGE BODY hierarchy
IS
  returnvalue VARCHAR2 (4000);
  FUNCTION branch
    (v_level     IN NUMBER,
     v_value     IN VARCHAR2,
     v_delimeter IN VARCHAR2 DEFAULT CHR (0))
    RETURN VARCHAR2
  IS
  BEGIN
    branchtable (v_level) := v_value;
    returnvalue := v_value;
    FOR i IN REVERSE 1 .. v_level - 1
    LOOP
      returnvalue := branchtable (i)
      || v_delimeter
      || returnvalue;
    END LOOP;
    RETURN returnvalue;
  END branch;
END hierarchy;
SELECT   id, parent_id, print_order, lvl
FROM     (SELECT     id, parent_id, print_order, LEVEL lvl,
                     hierarchy.branch (LEVEL, print_order) branch
          FROM       test_table
          START WITH parent_id IS NULL
          CONNECT BY PRIOR id = parent_id)
ORDER BY branch
        ID  PARENT_ID PRINT_ORDER        LVL
         1                      1          1
         6          1           1          2
         5          1           2          2
         2          1           3          2
         4          2           1          3
         3          2           2          3
6 rows selected.