Convert Non-Hierarchical data into Hierarchical data for Tree creation

Question

Hi guys,
I've been trying to figure this out for about two entire days now and I'm still stuck and see no possible solution which doesn't involve a new table creation.
Thing is that I want to create a Tree to navigate through Projects and Tasks, I'm using the "Task Manager" demo app, which I have customized a bit to fit my needs.
Basically I cannot create the Tree 'cause the relation between Projects and Tasks is not a hierarchical relation, it's a 1:N relation as this:
__Projects__
ID (PK)
PROJECT_NAME
___Tasks___
ID (PK)
PROJECT_ID (FK references Projects.ID)
So what I need to do is "force" that 1:N relation to a a hierarchical relation by creating a query (view) that joins the two tables into a single one and that have 2 columns I can use as ID and PARENT_ID for the tree creation.
This is the Data Model:
CREATE TABLE "EBA_TASK_PROJECTS"
(     "ID" NUMBER,
     "PROJECT_NAME" VARCHAR2(255),
     "CREATED_ON" DATE NOT NULL ENABLE,
     "CREATED_BY" VARCHAR2(255) NOT NULL ENABLE,
     "UPDATED_ON" DATE,
     "UPDATED_BY" VARCHAR2(255),
     "FLEX_01" VARCHAR2(4000),
     "FLEX_02" VARCHAR2(4000),
     "FLEX_03" VARCHAR2(4000),
     "FLEX_04" VARCHAR2(4000),
     "FLEX_05" VARCHAR2(4000),
     "PARENT_ID" NUMBER,
     "IS_ACTIVE" VARCHAR2(1),
     "DESCRIPTION" VARCHAR2(4000),
     CONSTRAINT "EBA_TASK_PROJECTS_ACTIVE_CC" CHECK (is_active in ('Y', 'N')) ENABLE,
     CONSTRAINT "EBA_TASK_PROJECTS_PK" PRIMARY KEY ("ID") ENABLE
) ;ALTER TABLE "EBA_TASK_PROJECTS" ADD CONSTRAINT "EBA_TASK_PROJECTS_FK" FOREIGN KEY ("PARENT_ID")
     REFERENCES "EBA_TASK_PROJECTS" ("ID") ON DELETE CASCADE ENABLE;
CREATE TABLE "EBA_TASK_TASKS"
(     "ID" NUMBER NOT NULL ENABLE,
     "PROJECT_ID" NUMBER NOT NULL ENABLE,
     "TASK_PRIORITY" VARCHAR2(400) NOT NULL ENABLE,
     "TASK_DIFFICULTY" VARCHAR2(400) NOT NULL ENABLE,
     "TASK_NAME" VARCHAR2(4000) NOT NULL ENABLE,
     "TASK_DETAILS" VARCHAR2(4000),
     "CREATED_ON" DATE NOT NULL ENABLE,
     "COMPLETED" DATE,
     "CREATED_BY" VARCHAR2(400) NOT NULL ENABLE,
     "STATUS" VARCHAR2(4000),
     "UPDATED_ON" DATE,
     "STARTED" DATE,
     "TASK_PREDEFINED_ID" NUMBER,
     "UPDATED_BY" VARCHAR2(255),
     "USER_NAME" VARCHAR2(255) NOT NULL ENABLE,
     "FLEX_01" VARCHAR2(4000),
     "FLEX_02" VARCHAR2(4000),
     "FLEX_03" VARCHAR2(4000),
     "FLEX_04" VARCHAR2(4000),
     "FLEX_05" VARCHAR2(4000),
     "PERCENTAGE" NUMBER,
     CONSTRAINT "EBA_TASK_TASKS_PK" PRIMARY KEY ("ID") ENABLE
) ;ALTER TABLE "EBA_TASK_TASKS" ADD CONSTRAINT "EBA_TASK_TASKS_PROJECTS_FK" FOREIGN KEY ("PROJECT_ID")
     REFERENCES "EBA_TASK_PROJECTS" ("ID") ON DELETE CASCADE ENABLE;
I'm using APEX4.0
That's pretty much it guys, hope you can help me with this. I'm really stuck on this and am about to give up.

Answer 1

WOW Odie! You're awesome !! It worked like a charm, I created a view as you suggested:
CREATE OR REPLACE FORCE VIEW "VIEW_TASKS_PROJECTS_TREE" ("ID", "PARENT_ID", "NODE_NAME") AS
SELECT to_char(id) as id
, null as parent_id
, project_name as node_name
FROM eba_task_projects
UNION ALL
SELECT to_char(id)
, to_char(project_id)
, task_name
FROM eba_task_tasks;
And then I created a new tree with the defaults and customized the Tree query a bit (just added the links really):
select case when connect_by_isleaf = 1 then 0
when level = 1 then 1
else -1
end as status,
level,
"NODE_NAME" as title,
null as icon,
"ID" as value,
null as tooltip,
'f?p=&APP_ID.:22:&SESSION.::NO::P22_ID,P22_PREV_PAGE:' || "ID" || ',3' as link
from "#OWNER#"."VIEW_TASKS_PROJECTS_TREE"
start with "PARENT_ID" is null
connect by prior "ID" = "PARENT_ID"
order siblings by "NODE_NAME"
Thanks man, you saved me a lot of time and headaches :)