Hierarchy Query to get parent nodes?

Question

Hi Everyone,
I want to write a hierarchy query which should give me the path starting from given node to its parents(Grand parents). below is the sample data and the output what i am expecting. and also the output what i am getting right now from my query.
CREATE TABLE RELATION (PARENT VARCHAR2(5),CHILD VARCHAR2(5) PRIMARY KEY);
--Data for the tree which starts from the root 'A'
Insert into RELATION (PARENT, CHILD) Values (NULL,'A');
Insert into RELATION (PARENT, CHILD) Values ('A', 'B');
Insert into RELATION (PARENT, CHILD) Values ('A', 'C');
Insert into RELATION (PARENT, CHILD) Values ('B', 'D');
Insert into RELATION (PARENT, CHILD) Values ('B', 'E');
Insert into RELATION (PARENT, CHILD) Values ('D', 'F');
Insert into RELATION (PARENT, CHILD) Values ('C', 'G');
--Data for the tree which starts from the root 'H'
Insert into RELATION (PARENT, CHILD) Values (NULL,'H');
Insert into RELATION (PARENT, CHILD) Values ('H', 'I');
Insert into RELATION (PARENT, CHILD) Values ('H', 'J');
Expected Output by passing values as 'F' which gives the path from bottom to up.
A<-B<-D<-F
My Query:
SELECT substr(sys_connect_by_path(child,'<-'),3)
FROM relation
WHERE connect_by_isleaf = 1
START WITH child = 'F'
CONNECT BY PRIOR parent = child
ORDER BY child;
Output of my query:
F<-D<-B<-A
I am getting the output in reverse order. i can use the reverse string function to reverse the string but the problem is the node can also contain the values like 'AC' 'BA'.. in future.
Can anyone please help me in getting the correct output.
Thank you in advance.

Answer 1

I like ListAgg :D
with RELATION(PARENT,CHILD) as(
select NULL,'A' from dual union all
select 'A', 'B' from dual union all
select 'A', 'C' from dual union all
select 'B', 'D' from dual union all
select 'B', 'E' from dual union all
select 'D', 'F' from dual union all
select 'C', 'G' from dual union all
select NULL,'H' from dual union all
select 'H', 'I' from dual union all
select 'H', 'J' from dual)
SELECT ListAgg(child,'<-')
       within group(order by Level desc) as revPath
FROM relation
START WITH child = 'F'
CONNECT BY PRIOR parent = child;
revPath
A<-B<-D<-F