SQL Movie-Rating

You've started a new movie-rating website, and you've been collecting data on reviewers' ratings of various movies. There's not much data yet, but you can still try out some interesting queries. Here's the schema:

Movie ( mID, title, year, director ) English: There is a movie with ID number mID, a title, a release year, and a director.

Reviewer ( rID, name ) English: The reviewer with ID number rID has a certain name.

Rating ( rID, mID, stars, ratingDate ) English: The reviewer rID gave the movie mID a number of stars rating (1-5) on a certain ratingDate.

SQL Social-Network

Students at your hometown high school have decided to organize their social network using databases. So far, they have collected information about sixteen students in four grades, 9-12. Here's the schema:

Highschooler ( ID, name, grade ) English: There is a high school student with unique ID and a given first name in a certain grade.

Friend ( ID1, ID2 ) English: The student with ID1 is friends with the student with ID2. Friendship is mutual, so if (123, 456) is in the Friend table, so is (456, 123).

Likes ( ID1, ID2 ) English: The student with ID1 likes the student with ID2. Liking someone is not necessarily mutual, so if (123, 456) is in the Likes table, there is no guarantee that (456, 123) is also present.