: Relational Algebra

Database schema:

LIKE$($person$,$ sport$),$ PRACTICE$($person$,$ sport$),$

where person and sport are keys in both tables. The table LIKE gives the sports a

person likes, the table PRACTICE gives the sports a person practices. We assume

that a person likes at least one sport and practices at least one sport. We assume

also that a person does not like a sport if the sport is not listed among the sports that

person likes.

The following queries are:

$1.$ List the people who like soccer.