Question: Which customers have both "On Road" and "Shipped" as order status? List the customer ids.
SQL: SELECT T1.customer_id FROM customers AS T1 JOIN orders AS T2 ON T1.customer_id = T2.customer_id WHERE T2.order_status = "On Road" INTERSECT SELECT T1.customer_id FROM customers AS T1 JOIN orders AS T2 ON T1.customer_id = T2.customer_id WHERE T2.order_status = "Shipped"