What are the addresses of customers living in Germany who have had an invoice?
SELECT DISTINCT T1.Address FROM CUSTOMER AS T1 JOIN INVOICE AS T2 ON T1.CustomerId  =  T2.CustomerId WHERE T1.country  =  "Germany"
addresses of customers living in Germany refers to T1.Address WHERE T1.country = 'Germany'; have had an invoice refers to JOIN INVOICE ON T1.CustomerId = T2.CustomerId;