Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE CUSTOMER (CustomerId VARCHAR, FirstName VARCHAR)
TABLE: CREATE TABLE INVOICE (InvoiceDate VARCHAR, CustomerId VARCHAR)

### Question ###
Find all invoice dates corresponding to customers with first name Astrid and last name Gruber.

### Accurate SQL ###

SELECT T2.InvoiceDate FROM CUSTOMER AS T1 JOIN INVOICE AS T2 ON T1.CustomerId = T2.CustomerId WHERE T1.FirstName = "Astrid" AND LastName = "Gruber"