Question

I have table as

+-------------+----------------------+--------------------+
| category_id | name                 | parent_category_id |
+-------------+----------------------+--------------------+
|           1 | Pizzas               |               NULL |
|           2 | Cheese Pizzas        |                  1 |
|           3 | Spicy Pizzas         |                  1 |
|           4 | Shakes               |               NULL |
|           5 | Milk Shakes          |                  4 |

I have only single level nesting and its going to be the same

I wish to retrieve the rows like

Pizza
   Cheese Pizzas
   Spicy Pizzas
Shakes
   Milk Shakes

Is there something like "Trees" In MySQL as in Oracle, I did read the article http://ftp.nchu.edu.tw/MySQL/tech-resources/articles/hierarchical-data.html

Changing the table structure seems more feasible when there is dynamic levels of nesting, for my case its just going to be 1 throughout

Any Suggestions?

Answer 1

You could use a self-join and do something like:

SELECT   parent.category_id, parent.name AS parent, child.name AS child
FROM     my_table parent JOIN my_table child
      ON parent.parent_category_id IS NULL
     AND child.parent_category_id = parent.category_id
ORDER BY parent.category_id, child.category_id

See it on sqlfiddle.

Or even group the results, if so desired:

SELECT   parent.name, GROUP_CONCAT(child.name ORDER BY child.category_id)
FROM     my_table parent JOIN my_table child
      ON parent.parent_category_id IS NULL
     AND child.parent_category_id = parent.category_id
GROUP BY parent.category_id
ORDER BY parent.category_id

See it on sqlfiddle.