Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE CUSTOMER (CustomerId VARCHAR, FirstName VARCHAR); CREATE TABLE INVOICE (InvoiceDate VARCHAR, CustomerId VARCHAR)
### Question:
Find all invoice dates corresponding to customers with first name Astrid and last name Gruber.
### Answer:
SELECT T2.InvoiceDate FROM CUSTOMER AS T1 JOIN INVOICE AS T2 ON T1.CustomerId = T2.CustomerId WHERE T1.FirstName = "Astrid" AND LastName = "Gruber"