Find all invoice dates corresponding to customers with first name Astrid and last name Gruber.
SELECT T2.InvoiceDate FROM CUSTOMER AS T1 JOIN INVOICE AS T2 ON T1.CustomerId  =  T2.CustomerId WHERE T1.FirstName  =  "Astrid" AND LastName  =  "Gruber"
SELECT T2.InvoiceDate FROM CUSTOMER AS T1 JOIN INVOICE AS T2 ON T1.CustomerId  =  T2.CustomerId WHERE T1.FirstName  =  "Astrid" AND LastName  =  "Gruber"
[{'InvoiceDate': '2009-12-08 00:00:00'}, {'InvoiceDate': '2010-01-18 00:00:00'}, {'InvoiceDate': '2010-09-18 00:00:00'}, {'InvoiceDate': '2012-04-24 00:00:00'}, {'InvoiceDate': '2012-07-27 00:00:00'}, {'InvoiceDate': '2012-10-29 00:00:00'}, {'InvoiceDate': '2013-06-19 00:00:00'}]