You have three tables, BOOKS, AUTHORS and BOOKAUTHORS. You want to show a listing of authors who have never written a book. Which of the following statement is correct?

SELECT lname$,$ fname, isbn

FROM authors LEFT OUTER JOIN bookauthors USING $($authorid$)$

LEFT OUTER JOIN books USING $($isbn$)$

WHERE isbn is NULL;

SELECT lname$,$ fname, isbn

FROM authors LEFT OUTER JOIN bookauthors USING $($authorid$)$

LEFT OUTER JOIN books USING $($isbn$)$

WHERE NOT EXISTS $($isbn$)$;

SELECT lname$,$ fname, isbn

FROM authors LEFT OUTER JOIN bookauthors USING $($authorid$)$

LEFT OUTER JOIN books USING $($isbn$)$

WHERE isbn $=$ 'NULL';

SELECT lname$,$ fname, isbn

FROM authors LEFT OUTER JOIN bookauthors USING $($authorid$)$

LEFT OUTER JOIN books USING $($isbn$)$

WHERE isbn $=$ NULL;