Question

I have a categories table and an items table. I have about 20 categories. In the items table there are items from 10 of those categories. I want to select all the categories that have items in the items table. I want to exclude all the categories that have no items.

The Items table has a categoryID field that matches the ID field of the category.

Answer 1

select * from categories c inner join items i on i.categoryID = c.id;

OR

select * from categories c where c.id in (select i.categoryID from items i);