Question

In my categories table I have: cat_id, cat_name, cat_slug.
In the table items I have: item_title, item_id, item_category.

`item_category` = `cat_id`

I’m using the following SQL to get “all” categories and how many items they have:

SELECT *, COUNT(`item_id`) 
FROM `menu_categories` 
    JOIN `menu_items` ON `item_category` = `cat_id` 
GROUP BY `item_category`

But it doesn’t show empty categories, i.e. categories without items.

Answer 1

You need to use LEFT JOIN instead of JOIN

SELECT *, COUNT(`item_id`) 
FROM `menu_categories`
  LEFT JOIN `menu_items` ON `item_category` = `cat_id`
GROUP BY `item_category`

Have a look at A Visual Explanation of SQL Joins.