php - MySQL SELECT Tree Parent IDs

Question

How can I sort the records of a SELECT statement so that they represent a valid tree?

All of my attempts show sub-nodes nested under wrong parent nodes. What is the most reliable way to achieve this ordering?

Data

ID      Parent ID      Title
--------------------------------------------
0       NULL           Root
1       0              Node A
2       0              Node B
3       1              Sub-Node C
4       1              Sub-Node D
5       3              Sub-Node E

Output

ID      Parent ID      Title
--------------------------------------------
0       NULL           Root
1       0              Node A
3       1              Sub-Node C
5       3              Sub-Node E
4       1              Sub-Node D
2       0              Node B

Data Visualisation

Root
    Node A
        Sub-Node C
            Sub-Node E
        Sub-Node D
    Node B

Answer 1

You can use Nested Sets. Check out this article:

Managing Hierarchical Data in MySQL

The author describes a few different methods for building hierarchies in SQL, complete with example queries. It's a very good read about this subject!