CREATE TABLE genre (genreid NUMBER, name CLOB)
CREATE TABLE playlisttrack (playlistid NUMBER, trackid NUMBER)
CREATE TABLE album (albumid NUMBER, title CLOB, artistid NUMBER)
CREATE TABLE invoiceline (invoicelineid NUMBER, invoiceid NUMBER, trackid NUMBER, unitprice NUMBER, quantity NUMBER)
CREATE TABLE track (trackid NUMBER, name CLOB, albumid NUMBER, mediatypeid NUMBER, genreid NUMBER, composer CLOB, milliseconds NUMBER, bytes NUMBER, unitprice NUMBER)
CREATE TABLE invoice (invoiceid NUMBER, customerid NUMBER, invoicedate TIME, billingaddress CLOB, billingcity CLOB, billingstate CLOB, billingcountry CLOB, billingpostalcode CLOB, total NUMBER)
CREATE TABLE employee (employeeid NUMBER, lastname CLOB, firstname CLOB, title CLOB, reportsto NUMBER, birthdate TIME, hiredate TIME, address CLOB, city CLOB, state CLOB, country CLOB, postalcode CLOB, phone CLOB, fax CLOB, email CLOB)
CREATE TABLE mediatype (mediatypeid NUMBER, name CLOB)
CREATE TABLE playlist (playlistid NUMBER, name CLOB)
CREATE TABLE artist (artistid NUMBER, name CLOB)
CREATE TABLE customer (customerid NUMBER, firstname CLOB, lastname CLOB, company CLOB, address CLOB, city CLOB, state CLOB, country CLOB, postalcode CLOB, phone CLOB, fax CLOB, email CLOB, supportrepid NUMBER)

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" "T1" JOIN "invoice" "T2" ON "T1"."customerid" = "T2"."customerid" WHERE "Astrid" = "T1"."firstname" AND "Gruber" = "lastname"