I have been trying to use the GROUP BY function and I am getting in front of a wall!!
I am pulling an element from a table as first category and check at the same time if there is any second category associated to the first one. If none, the first category links to the items under that category.
If there is a second category associated to the first category, I want these second categories to be display under the first category using the "while" loop.
Problem, for some first categories which have second categories, it works fine (meaning it displays the second categories within the loop), for some other first categories, it does not show the second categories...