1. Run the query in the editor. Which column does the error name?
2. Fix it: show each country and the number of customers from it.
3. Show each order status and the number of orders with it. Most orders first; when two counts are the same, sort by status from A to Z.
4. Show each category_id and the total stock of the products in it. Look for the group of the product with no category.
5. Show each department_id and the average salary of its employees, rounded to 2 decimal places.