CREATE TABLE customer_orders (order_id VARCHAR, order_date INT)
CREATE TABLE order_items (order_quantity INT, order_id VARCHAR)

Find the total amount of products ordered before 2018-03-17 07:13:53.
SELECT SUM(t2.order_quantity) FROM customer_orders AS t1 JOIN order_items AS t2 ON t1.order_id = t2.order_id WHERE t1.order_date < "2018-03-17 07:13:53"
SELECT SUM("t2"."order_quantity") FROM "customer_orders" AS "t1" JOIN "order_items" AS "t2" ON "t1"."order_id" = "t2"."order_id" WHERE "2018-03-17 07:13:53" > "t1"."order_date"