SELECT AVG(order_total) AS avg_order_value FROM orders; 
-- Output:
avg_order_value
---------------
    $127.35

SELECT product_id, AVG(rating) AS avg_rating FROM reviews GROUP BY product_id; 
-- Output:
product_id    avg_rating
----------    ----------
A101            4.2
B205            3.8
C333            4.7
D444            4.1
E555            4.9

SELECT AVG(DISTINCT price) AS avg_unique_price FROM products;
-- Output:
avg_unique_price
----------------
     $75.49

(Calculated from unique prices:
 19.99, 29.99, 49.99, 89.99, 
 99.99, 149.99, 199.99)