Find all invoice dates corresponding to customers with first name Astrid and last name Gruber.
create table customer (customerid varchar, firstname varchar, PRIMARY KEY (customerid)); create table invoice (invoicedate varchar, customerid varchar, PRIMARY KEY (invoicedate))
select t2.invoicedate from customer as t1 join invoice as t2 on t1.customerid = t2.customerid where t1.firstname = "astrid" and lastname = "gruber"