Below is a commercial system to demonstrate SQL, where you can type in queries using online forms:

Interactive SQL tutorial and demonstration

Please try a few exercises. Section 11 contains the interactive form, and links to the two tables:

• customers(customerid, firstname, lastname, city, state)
• items_ordered(customerid, order_date, item, quantity, price)

Note that this SQL interpreter does not support sub-SELECT statements or all SQL operators.

Write queries for the following (note that you can run the SQL query real-time in the dialog box at the bottom of each page):

• Retrieve the total amount purchased by each customer, ordered by the customer with the highest total first.
• Retrieve customers (firstname, lastname) from Arizona or Oregon that made purchases over $20.
• If a customer made single orders of $20-$50, we will apply a discount of 10%. However, if a customer made a single order >$50, we will apply a flat discount of $10. Retrieve the customers who qualify for such discounts and display their order price and order price after discounts were applied. (this can be done as 2 separate queries. How would you do it in one?)