List the names of all the distinct customers who bought a keyboard.
CREATE TABLE order_items (order_id VARCHAR, product_id VARCHAR); CREATE TABLE customers (customer_name VARCHAR, customer_id VARCHAR); CREATE TABLE products (product_id VARCHAR, product_name VARCHAR); CREATE TABLE customer_orders (customer_id VARCHAR, order_id VARCHAR)
[SQL] SELECT DISTINCT T1.customer_name FROM customers AS T1 JOIN customer_orders AS T2 ON T1.customer_id = T2.customer_id JOIN order_items AS T3 ON T2.order_id = T3.order_id JOIN products AS T4 ON T3.product_id = T4.product_id WHERE T4.product_name = "keyboard" [/SQL]