Stanford--Introduce to Databases(1)

For each movie that has at least one rating, find the highest number of stars that movie received. Return the movie title and number of stars. Sort by movie title.
SQL Movie-Rating Query Exercises (core set)

 

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, atitle, a releaseyear, and adirector.

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

  Rating ( rID, mID, stars, ratingDate )
  English: The reviewer rID  gave the moviemID a number ofstars rating (1-5) on a certainratingDate.

  Learn more.Discuss

Movie

mID	title	year	director
101	Gone with the Wind	1939	Victor Fleming
102	Star Wars	1977	George Lucas
103	The Sound of Music	1965	Robert Wise
104	E.T.	1982	Steven Spielberg
105	Titanic	1997	James Cameron
106	Snow White	1937	<null>
107	Avatar	2009	James Cameron
108	Raiders of the Lost Ark	1981	Steven Spielberg

Reviewer

rID	name
201	Sarah Martinez
202	Daniel Lewis
203	Brittany Harris
204	Mike Anderson
205	Chris Jackson
206	Elizabeth Thomas
207	James Cameron
208	Ashley White

Rating

rID	mID	stars	ratingDate
201	101	2	2011-01-22
201	101	4	2011-01-27
202	106	4	<null>
203	103	2	2011-01-20
203	108	4	2011-01-12
203	108	2	2011-01-30
204	101	3	2011-01-09
205	103	3	2011-01-27
205	104	2	2011-01-22
205	108	4	<null>
206	107	3	2011-01-15
206	106	5	2011-01-19
207	107	5	2011-01-20
208	104	3	2011-01-02

 

Question 1

Find the titles of all movies directed by Steven Spielberg.

select title from Movie where director='Steven Spielberg'

Question 2

Find all years that have a movie that received a rating of 4 or 5, and sort them in increasing order.

select year from Movie where mID in (select mID from Rating where stars in (4, 5)) order by year;

 

Question 3

Find the titles of all movies that have no ratings.

select title from Movie where mID not in (select mID from Rating)

 

Question 4

Some reviewers didn't provide a date with their rating. Find the names of all reviewers who have ratings

 

with a NULL value for the date.

 select distinct name from Reviewer natural join Rating where ratingDate is null

 

Question 5

Write a query to return the ratings data in a more readable format: reviewer name, movie title, stars, and

 

ratingDate. Also, sort the data, first by reviewer name, then by movie title, and lastly by number of stars.

select name, title, stars, ratingDate from (Movie natural join Reviewer) natural join  Rating order by name, title, stars

 

Question 6

For all cases where the same reviewer rated the same movie twice and gave it a higher rating the second

 

time, return the reviewer's name and the title of the movie.

select name, title from Reviewer natural join Movie where rID in (select rID from ((select * from Rating R1 where rID in (select rID from Rating R2 group by rID, mID having count(stars)=2) and exists (select * from Rating R3 where R3.rID=R1.rID and R3.mID=R1.mID and R3.ratingDate>R1.ratingDate and R3.stars>R1.stars)) as Rs)) and mID in (select mID from ((select * from Rating R1 where rID in (select rID from Rating R2 group by rID, mID having count(stars)=2) and exists (select * from Rating R3 where R3.rID=R1.rID and R3.mID=R1.mID and R3.ratingDate>R1.ratingDate and R3.stars>R1.stars)) as Rs))

 

Question 7

For each movie that has at least one rating, find the highest number of stars that movie received. Return

 

the movie title and number of stars. Sort by movie title.