What is the placement date of the order whose invoice number is 10?
create table orders (date_order_placed varchar, order_id varchar, PRIMARY KEY (date_order_placed)); create table shipments (order_id varchar, invoice_number varchar, PRIMARY KEY (order_id))
select t1.date_order_placed from orders as t1 join shipments as t2 on t1.order_id = t2.order_id where t2.invoice_number = 10