CREATE TABLE orders (date_order_placed VARCHAR(255), order_id VARCHAR(255)); CREATE TABLE shipments (order_id VARCHAR(255), invoice_number VARCHAR(255))
What is the placement date of the order whose invoice number is 10?
    
SQL: 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