Oracle return tree having all combinations - sql

Question

I need a query that will return all women within the group.
Example data table (Oracle 11g):
with t as (
select 'K' as GROUP_NAME, 1 as ELEMENT_ID from dual
union
select 'K' as GROUP_NAME, 2 as ELEMENT_ID from dual
union
select 'K' as GROUP_NAME, 3 as ELEMENT_ID from dual
union
select 'L' as GROUP_NAME, 1 as ELEMENT_ID from dual
union
select 'L' as GROUP_NAME, 2 as ELEMENT_ID from dual
union
select 'L' as GROUP_NAME, 3 as ELEMENT_ID from dual
union
select 'P' as GROUP_NAME, 1 as ELEMENT_ID from dual
union
select 'P' as GROUP_NAME, 2 as ELEMENT_ID from dual
union
select 'P' as GROUP_NAME, 3 as ELEMENT_ID from dual
)
select * from t
K 1
K 2
K 3
L 1
L 2
L 3
P 1
P 2
P 3
I need to generate a tree with all the combinations without repeating them in groups (group K, L, P)
A tree must not contain a group of trees, i.e. there must not be a tree with such a branch: K1->L1->K2
K1
+-- L1
+-- P1
+-- P2
+-- P3
+-- L2
+-- P1
+-- P2
+-- P3
+-- L3
+-- P1
+-- P2
+-- P3
K2
+-- L1
+-- P1
+-- P2
+-- P3
+-- L2
+-- P1
+-- P2
+-- P3
+-- L3
+-- P1
+-- P2
+-- P3
K3
+-- L1
+-- P1
+-- P2
+-- P3
+-- L2
+-- P1
+-- P2
+-- P3
+-- L3
+-- P1
+-- P2
+-- P3
L1
+-- K1
+-- P1
+-- P2
+-- P3
+-- K2
....

Answer 1

SELECT ltrim(sys_connect_by_path(group_name || element_id,'-'),'-') FROM t
START WITH t.group_name = 'K'
CONNECT BY ( t.group_name = 'L' AND PRIOR t.group_name = 'K' ) OR ( t.group_name = 'P'
AND PRIOR t.group_name = 'L');
+-----------+
| TREE_PATH |
+-----------+
| K1 |
| K1-L1 |
| K1-L1-P1 |
| K1-L1-P2 |
| K1-L1-P3 |
| K1-L2 |
| K1-L2-P1 |
| K1-L2-P2 |
| K1-L2-P3 |
| K1-L3 |
| K1-L3-P1 |
| K1-L3-P2 |
| K1-L3-P3 |
| K2 |
| K2-L1 |
| K2-L1-P1 |
| K2-L1-P2 |
| K2-L1-P3 |
| K2-L2 |
| K2-L2-P1 |
| K2-L2-P2 |
| K2-L2-P3 |
| K2-L3 |
| K2-L3-P1 |
| K2-L3-P2 |
| K2-L3-P3 |
| K3 |
| K3-L1 |
| K3-L1-P1 |
| K3-L1-P2 |
| K3-L1-P3 |
| K3-L2 |
| K3-L2-P1 |
| K3-L2-P2 |
| K3-L2-P3 |
| K3-L3 |
| K3-L3-P1 |
| K3-L3-P2 |
| K3-L3-P3 |
+-----------+
If you didn't want a tree and just wanted all combinations, that would be a 'CROSS JOIN'. Like so:
select * from t k CROSS JOIN t l CROSS JOIN t p
where k.group_name = 'K'
AND l.group_name = 'L'
and p.group_name = 'P'
+------------+------------+--------------+--------------+--------------+--------------+
| GROUP_NAME | ELEMENT_ID | GROUP_NAME_1 | ELEMENT_ID_1 | GROUP_NAME_2 | ELEMENT_ID_2 |
+------------+------------+--------------+--------------+--------------+--------------+
| K | 1 | L | 1 | P | 1 |
| K | 1 | L | 1 | P | 2 |
| K | 1 | L | 1 | P | 3 |
| K | 1 | L | 2 | P | 1 |
| K | 1 | L | 2 | P | 2 |
| K | 1 | L | 2 | P | 3 |
| K | 1 | L | 3 | P | 1 |
| K | 1 | L | 3 | P | 2 |
| K | 1 | L | 3 | P | 3 |
| K | 2 | L | 1 | P | 1 |
| K | 2 | L | 1 | P | 2 |
| K | 2 | L | 1 | P | 3 |
| K | 2 | L | 2 | P | 1 |
| K | 2 | L | 2 | P | 2 |
| K | 2 | L | 2 | P | 3 |
| K | 2 | L | 3 | P | 1 |
| K | 2 | L | 3 | P | 2 |
| K | 2 | L | 3 | P | 3 |
| K | 3 | L | 1 | P | 1 |
| K | 3 | L | 1 | P | 2 |
| K | 3 | L | 1 | P | 3 |
| K | 3 | L | 2 | P | 1 |
| K | 3 | L | 2 | P | 2 |
| K | 3 | L | 2 | P | 3 |
| K | 3 | L | 3 | P | 1 |
| K | 3 | L | 3 | P | 2 |
| K | 3 | L | 3 | P | 3 |
+------------+------------+--------------+--------------+--------------+--------------+