Recursive tables (grouping items)

Question

I have a requirement to allow Users to create groups of items and groups of groups of items( via web interface). [Any item can fall under any number of groups and any group can fall within any number of groups]
I planned to use 2 recursive tables, but I want to see if there are alternative solutions. [This also has to be flexible enough to work with Oracle and mysql]
Also, if anyone has examples for the interface(using jsp), those are greatly appreciated.
Any comments are welcome.
Thanks in advance!

Answer 1

I meant a table that has a foreign key which points to itself, but I would use 1 table (not 2 as I mentioned earlier).
Another way of looking at it using Roles/Users vs. Groups/Item:
(Probably making it muddier, but here it goes)
For Example:
Role Table
role_id parent_id(references role_id)
A          null
B          null
C          A
D          C
D          B [note Group D is child of group C and B]
E          null
RoleUserMap Table
role_id          user_id
A          1
A          2
A          3
B          4
B          5
C          6
C          7
C          8
D          9
D          10
D          11
E          1
E          2
E          3
E          4
E          5
E          11
User Table
user_id          name
1          John
2          Jane     
3          Mary
4          Bob
5          Stephanie
6          Bill
7          Liz
8          Kim
9          David
10          Ann
11          Susan