Stuff

mysql> select * from categories order by path, name;
+----+---------------+--------------------------+------------+------------+
| id | name          | path                     | created_at | updated_at |
+----+---------------+--------------------------+------------+------------+
|  2 | Cars          | /                        | NULL       | NULL       | 
|  1 | Entertainment | /                        | NULL       | NULL       | 
|  3 | Gasoline      | /Cars                    | NULL       | NULL       | 
|  6 | Parts         | /Cars                    | NULL       | NULL       | 
|  4 | Green Gas     | /Cars/Gasoline           | NULL       | NULL       | 
|  8 | Light Gas     | /Cars/Gasoline           | NULL       | NULL       | 
|  5 | Soja Based    | /Cars/Gasoline/Green Gas | NULL       | NULL       | 
|  7 | Pieces        | /Cars/Parts              | NULL       | NULL       | 
+----+---------------+--------------------------+------------+------------+

My issue is, I would like to have this (Please note the difference 
for pleaces having path = /), actually Ineed a "tree":
+----+---------------+--------------------------+------------+------------+
| id | name          | path                     | created_at | updated_at |
+----+---------------+--------------------------+------------+------------+
|  2 | Cars          | /                        | NULL       | NULL       | 
|  3 | Gasoline      | /Cars                    | NULL       | NULL       | 
|  6 | Parts         | /Cars                    | NULL       | NULL       | 
|  4 | Green Gas     | /Cars/Gasoline           | NULL       | NULL       | 
|  8 | Light Gas     | /Cars/Gasoline           | NULL       | NULL       | 
|  5 | Soja Based    | /Cars/Gasoline/Green Gas | NULL       | NULL       | 
|  7 | Pieces        | /Cars/Parts              | NULL       | NULL       | 
|  1 | Entertainment | /                        | NULL       | NULL       | 
+----+---------------+--------------------------+------------+------------+