how many customers live in germany and have invoice
select count ( * ) from customer as t1 join invoice as t2 on t1.customerid = t2.customerid where t1.country = "Germany"
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select t1.address from customer as t1 join invoice as t2 on t1.customerid = t2.customerid where t1.country = "Germany"
include the first and last name of customers of this address in the table
select t1.address,t1.firstname,t1.lastname from customer as t1 join invoice as t2 on t1.customerid = t2.customerid where t1.country = "Germany"