SELECT publisher FROM book_club WHERE YEAR  =  1989 INTERSECT SELECT publisher FROM book_club WHERE YEAR  =  1990
What are the publishers who have published a book in both 1989 and 1990?
SELECT publisher FROM book_club WHERE YEAR = 1989 INTERSECT SELECT publisher FROM book_club WHERE YEAR = 1990
select publisher from book_club where year = value intersect select publisher from book_club where year = value
What are the publishers who have published a book in both 1989 and 1990 ?