CREATE TABLE orders (order_id NUMBER, customer_id NUMBER, order_status CLOB, date_order_placed TIME, order_details CLOB)
CREATE TABLE order_items (order_item_id NUMBER, product_id NUMBER, order_id NUMBER, order_item_status CLOB, order_item_details CLOB)
CREATE TABLE customers (customer_id NUMBER, customer_name CLOB, customer_details CLOB)
CREATE TABLE invoices (invoice_number NUMBER, invoice_date TIME, invoice_details CLOB)
CREATE TABLE products (product_id NUMBER, product_name CLOB, product_details CLOB)
CREATE TABLE shipments (shipment_id NUMBER, order_id NUMBER, invoice_number NUMBER, shipment_tracking_number CLOB, shipment_date TIME, other_shipment_details CLOB)
CREATE TABLE shipment_items (shipment_id NUMBER, order_item_id NUMBER)

What are the names of the customers who bought product 'food' at least once?
SELECT T1.customer_name FROM customers AS T1 JOIN orders AS T2 JOIN order_items AS T3 JOIN products AS T4 ON T1.customer_id = T2.customer_id AND T2.order_id = T3.order_id AND T3.product_id = T4.product_id WHERE T4.product_name = "food" GROUP BY T1.customer_id HAVING COUNT(*) >= 1
SELECT "T1"."customer_name" FROM "customers" "T1" CROSS JOIN "order_items" "T3" JOIN "orders" "T2" ON "T1"."customer_id" = "T2"."customer_id" AND "T2"."order_id" = "T3"."order_id" JOIN "products" "T4" ON "T3"."product_id" = "T4"."product_id" AND "T4"."product_name" = "food" GROUP BY "T1"."customer_id" HAVING COUNT(*) >= 1