[GENERAL] Tree structure

[Kaare Rasmussen]

I can't figure this one out. I need a tree structure like this

Number  Pointer
1            0
2            1
3            1
4            2
5            0
6            1
7            5

This should somehow show up like this
Number
1
2
4
3
6
5
7

The whole excercise is because I'd like to show a tree structure:

1
- 2
- - 4
- 3
- 6
5
- 7

Is this possible with PostgreSQL?