/*
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 distinct year from movie,rating where movie.mid=rating.mid and 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 in
(
select mid from Movie except
select mid from rating )
select title from movie except
select title from movie,rating where movie.mid=rating.mid
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 name from reviewer,rating where reviewer.rid=rating.rid and 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,rating,reviewer where movie.mid=rating.mid and reviewer.rid=rating.rid 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 rating as F,Rating as S,Movie,Reviewer where F.rID=S.rID and F.mID=S.mID and F.stars
and F.ratingDate
select name,title from movie,reviewer,
( select r1.rid,r1.mid from rating as r1,rating as r2 where r1.rid=r2.rid and r1.mid=r2.mid and r1.ratingdate>r2.ratingdate and r1.stars>r2.stars) as r
where movie.mid=r.mid and reviewer.rid=r.rid
Question 7:For each movie, find the highest number of stars that movie received as a rating.Return the movie title and number of stars.Sort by movie title.
select title,MAX(stars) as max_star from rating,Movie
where Rating.mID=Movie.mID group by title order by title
select title,maxrating from movie,
(select mid,max(stars) as maxrating from rating group by mid) as r where movie.mid=r.mid order by title
Question 8:For each movie, return the title and the ‘rating spread(范围)', that is, the difference between highest and lowest ratings given to that movie.Sort by rating spread from highest to lowest, then by movie title.
select title,MAX(stars)-MIN(stars) as rating_spread from rating,Movie
where Rating.mID=Movie.mID group by title
order by rating_spread desc,title
select title,spread as "rating spread"
from movie, (select mid,max(stars)-min(stars) as spread from rating group by mid) as r where movie.mid=r.mid order by spread desc,title
Question 9:Find the difference between the average rating of movies released before 1980 and the average rating of movies released after 1980.
(Make sure to calculate the average rating for each movie, then the average of those averages for movies before 1980 and movies after.Don't just calculate the overall average rating before and after 1980.)
select F.avg_star - S.avg_star from
,
(
select AVG(avg_star) as avg_star from (
select Rating.mID,AVG(stars) as avg_star
from Rating left join Movie on Rating.mID=Movie.mID where year>=1980 group by Rating.mID ) as S (
select AVG(avg_star) as avg_star from (
select Rating.mID,AVG(stars) as avg_star
from Rating left join Movie on Rating.mID=Movie.mID where year
) as F
) as S
select r1979.avgm-r1980.avgm from
,
Question 10:Add the reviewer Roger Ebert to your database, with an rID of 209.
insert into Reviewer values (209,'Roger Ebert')
Question 11:
Insert 5-star ratings by James Cameron for all movies in the database.Leave the review date as NULL.
insert into Rating(rID,mID,stars) select rid,mID,5 as stras from movie,
(select rid from Reviewer where name='James Cameron') as T
insert into rating(rid,mid,stars) select rid,mid,5 from reviewer,movie where name='James Cameron'
Question 12:For all movies that have an average rating of 4 stars or higher, add 25 to the release year.
(Update the existing tuples; don't insert new tuples.)
update Movie set year=year+25 (select sum(avgrating)/count(*) as avgM from
(select avg(stars) as avgrating from rating,movie where movie.mid=rating.mid and year>=1980 group by movie.mid) (select sum(avgrating)/count(*) as avgM from
(select avg(stars) as avgrating from rating,movie where movie.mid=rating.mid and year
as r)
as r1979
as r)
as r1980 where mID in
(select mID from Rating group by mID having AVG(stars)>=4)
*/
