Suppose we have a database consisting of the following three relations.
FREQUENTS(student, parlor) giving the parlors each student visits. SERVES(parlor, ice-cream) indicating what kind of ice-creams each parlor serves. LIKES(student, ice-cream) indicating what ice-creams each parlor serves. (Assuming that each student likes at least one ice-cream and frequents at least one parlor)
Express the following in SQL:
Print the students that frequent at least one parlor that serves some ice-cream that they like.
SELECT DISTINCT FREQUENTS.student FROM FREQUENTS, SERVES, LIKES WHERE FREQUENTS.parlor=SERVES.parlor AND SERVES.ice-cream=LIKES.ice-cream AND FREQUENTS.student=LIKES.student;