I just got a question, since you say in the #3:

How many orders did each customer make? Use the items_ordered table. Select the customerid, number of orders they made, and the sum of their orders if they purchased more than 1 item.
Exercise #3
and the answer you give is:

Code:
SELECT customerid, count(customerid), sum(price)
FROM items_ordered
GROUP BY customerid
HAVING count(customerid) > 1;
but shouldn't it be:

Code:
SELECT customerid, count(customerid), sum(price)
FROM items_ordered
GROUP BY customerid
HAVING count(quantity) > 1;
since you say if they purchased more then 1 item, but you count the number of times they ordered not the number of items they bought, don't know if i'm wrong or i found some liddle error