You have been given two tables, CUSTOMER and SALE. Currently…

You have been given two tables, CUSTOMER and SALE. Currently there is no foreign key relationship, but you want to add one, so you need to check the referential integrity constraint: SALE.CustomerNumber must exist in CUSTOMER.CustomerNumberYou run the following SQL query: SELECT CustomerNumber FROM SALE WHERE CustomerNumber NOT IN (SELECT CustomerNumber FROM CUSTOMER); What is shown in the results of this query?