Task: Text to Code
Input (English): Step 1: For each row in Customer_Orders table, find the corresponding rows in Invoices table.
Step 2: find Order_Date of the results of step 1 whose Order_Quantity equals 1
Output (English): SELECT T1.Order_Date FROM Customer_Orders AS T1 JOIN Invoices AS T2 ON T1.Order_ID = T2.Order_ID WHERE T2.Order_Quantity = 1