Select on a tree structure...

Question

Hi Guys,
I have the following tree structure where I want to perform a select to get the below results.
All Nodes are starting from D and types of the nodes are from A, (If a particular node is not connected to a type then it has its parent's type. ex.:- D11 is on A1 type)
..........................D1.(A1)
............................|
......|............|.................|...............|
.....D11......D12..........D13(A3).......D14
...................|.................................|
..............----------...........................D141(A4)
..............|.........|............................|
......D121(A1)...D122.................-------------
........................|......................|............|
..............D1221(A2)............D1411(A4)..D1412
........................|
..................|............|
..........D12211.........D12212
...............................|
.............................D122121
Selection can only be performed in D1, D1221, D13 and D141 nodes.
Perform selection on D1 should return - D11, D121 and D1221 (select lowest level nodes if they are in the same type and if the type of the node is changing then select the first node with the different type)
Perform selection on D1221 will return - D12211 and D122121
Perform selection on D13 will return null
Perform selection on D141 will return - D1411 and D1412
Table structure
seq_no...parent_seq_no...type
..D1................................A1
..D11..........D1........
..D13..........D1................A3
..D1221......D122.............A2
..D12211....D1221.....
..D1411......D141.............A4
Many Thanks and sorry for the long explanation,
Napster

Answer 1

Hi Frank,
Wow it sounds so simple. I was sort of lost with the connected by clause. Now it’s getting clear. Thanks!
One last question... can I used the connected by clause to get the top most node of a set of same type nodes. I used the connected by clause and wrote a function and it returns the exact output I need but it looks little messy. I will try to explain the requirement using the above example tree structure…
In the above example,
If I perform function on,
D1, it should return D1
D11, it should return D1
D121, it should return D1
D122121, it should return D1221
D13 should return D13 itself,
D 141 should return D141 itself,
D 1411 should return D141… etc.
The function I wrote….
FUNCTION Get_Root_Node__ (
   seq_no_ IN NUMBER ) RETURN NUMBER
IS
   CURSOR get_parent_list (seq_no_ NUMBER) IS  
      SELECT t.seq_no, t.type_cd
      FROM table_x t
      CONNECT BY PRIOR t.parent_seq_no = t.seq_no
      START WITH t.seq_no= seq_no_;
   CURSOR get_curr_list (seq_no_ NUMBER) IS  
      SELECT t.seq_no, t.type_cd
      FROM table_x t
      CONNECT BY PRIOR t.parent_seq_no = t.seq_no
      START WITH t.seq_no= seq_no_;
   top_seq_no_       NUMBER;
   cur_type_cd_      NUMBER;
BEGIN
   FOR parent_rec_ IN get_parent_list(seq_no_) LOOP
        IF (parent_rec_.type_cd IS NOT NULL) THEN
          IF (cur_type_cd_ IS NOT NULL) AND (parent_rec_.type_cd_ <> cur_type_cd_) THEN
             RETURN top_seq_no_;
          ELSE
             cur_type_cd_ := parent_rec_.type_cd_;
          END IF;
       ELSIF (cur_type_cd_ IS NOT NULL) THEN
          FOR curr_rec_ IN get_curr_list(parent_rec_.seq_no) LOOP
             IF (curr_rec_.type_cd IS NOT NULL) THEN
                IF curr_rec_.type_cd = cur_type_cd_ THEN
                   top_seq_no_ := curr_rec_.seq_no;
                ELSE
                   RETURN top_seq_no_;
                END IF;
             END IF;
          END LOOP;
       END IF;
       top_seq_no_ := parent_rec_.seq_no;
   END LOOP;
   RETURN top_seq_no_;
END Get_Root_Node__;Is it possible to get this done by a simple select?