A hierarchical query - how do I do

From: oracle_doc <nilendu_at_nilendu.com>
Date: 17 Feb 2006 20:53:06 -0800
Message-ID: <1140238386.406796.203000@o13g2000cwo.googlegroups.com>

I have two tables TASKS and TASK_PREDECESSORS

CREATE TABLE TASKS
(

  ID         NUMBER                             NOT NULL,
  NAME       VARCHAR2(200 BYTE)                 NOT NULL,

  PARENT_ID NUMBER
);

ID	NAME	PARENT_ID
1	A
2	a	1
3	b	1

CREATE TABLE TASK_PREDECESSORS
(

  PREDECESSOR_ID  NUMBER                        NOT NULL,
  SUCCESSOR_ID    NUMBER                        NOT NULL

);

PREDECESSOR_ID	SUCCESSOR_ID
2	3

I am looking for a query that returns all tasks in an oder that holds the following:

(1) children before parents
(2) predecessors before successors

i.e. the data in the table should return [ a, b, A ] - it should also generate an error or indicator
that detects a cycle.

I'm offering my apology ahead if this is a sheer waste of time for others. May be, I am missing something really obvious here and I'm still trying this.

Would really appreciate if anyone can offer a tip.

Thanks.

P.S. - This is not a homework. But yes, something I am working on.. Received on Fri Feb 17 2006 - 22:53:06 CST