Question

I have a table vm_category in which I fetch all rows from the category_id and caregory_name columns. I then use this in a drop-down to populate a search-filter module on the left side of the side.

Now doing so gives me a gigantic list of categories, and I’d like to narrow it down by category’s sub-category. Those are organized in another table called vm_category_xref in which I have 3 columns;

• category_parent_id
• category_child_id
• category_list

What I’d like to do is specify in my query to only return the category_id and names that match a specific category_parent_id in the _xref table. Here is my current query:

$query = "SELECT `c`.`category_name` AS `name` , `c`.`category_id` AS `id`
          FROM `#__vm_category` AS `c` ORDER BY `c`.`category_id`;";

I am not familiar with JOIN enough to figure this out, but I know it should be rather simple, and any help would be much appreciated. Thank you!

Answer 1

Try this:

SELECT 
    c.category_name AS name, 
    c.category_id AS id
FROM #__vm_category AS c 
    INNER JOIN vm_category_xref xr
    ON xr.category_child_id = c.category_id
WHERE xr.category_parent_id = 5 /* the parent_id you want to filter on */
ORDER BY c.category_id;