create database MovieRating;
use MovieRating;


/* Delete the tables if they already exist */
drop table if exists Movie;
drop table if exists Reviewer;
drop table if exists Rating;

/* Create the schema for our tables */
create table Movie(mID int, title text, year int, director text);
create table Reviewer(rID int, name text);
create table Rating(rID int, mID int, stars int, ratingDate date);

/* Populate the tables with our data */
insert into Movie values(101, 'Gone with the Wind', 1939, 'Victor Fleming');
insert into Movie values(102, 'Star Wars', 1977, 'George Lucas');
insert into Movie values(103, 'The Sound of Music', 1965, 'Robert Wise');
insert into Movie values(104, 'E.T.', 1982, 'Steven Spielberg');
insert into Movie values(105, 'Titanic', 1997, 'James Cameron');
insert into Movie values(106, 'Snow White', 1937, null);
insert into Movie values(107, 'Avatar', 2009, 'James Cameron');
insert into Movie values(108, 'Raiders of the Lost Ark', 1981, 'Steven Spielberg');

insert into Reviewer values(201, 'Sarah Martinez');
insert into Reviewer values(202, 'Daniel Lewis');
insert into Reviewer values(203, 'Brittany Harris');
insert into Reviewer values(204, 'Mike Anderson');
insert into Reviewer values(205, 'Chris Jackson');
insert into Reviewer values(206, 'Elizabeth Thomas');
insert into Reviewer values(207, 'James Cameron');
insert into Reviewer values(208, 'Ashley White');

insert into Rating values(201, 101, 2, '2011-01-22');
insert into Rating values(201, 101, 4, '2011-01-27');
insert into Rating values(202, 106, 4, null);
insert into Rating values(203, 103, 2, '2011-01-20');
insert into Rating values(203, 108, 4, '2011-01-12');
insert into Rating values(203, 108, 2, '2011-01-30');
insert into Rating values(204, 101, 3, '2011-01-09');
insert into Rating values(205, 103, 3, '2011-01-27');
insert into Rating values(205, 104, 2, '2011-01-22');
insert into Rating values(205, 108, 4, null);
insert into Rating values(206, 107, 3, '2011-01-15');
insert into Rating values(206, 106, 5, '2011-01-19');
insert into Rating values(207, 107, 5, '2011-01-20');
insert into Rating values(208, 104, 3, '2011-01-02');


-- 1.Find the titles of all movies directed by Steven Spielberg.
SELECT title AS 'Movies By Spielberg'
FROM Movie
WHERE director="Steven Spielberg";

-- 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
WHERE mID in (SELECT mID
			  FROM rating
              WHERE stars>3)
ORDER BY (year);

-- 3.Find the titles of all movies that have no ratings
SELECT DISTINCT(title) AS 'Titles with no ratings'
FROM Movie
WHERE mID in (SELECT mID
			  FROM Movie
              WHERE mID
			  NOT IN(SELECT mID
					 FROM Rating));

-- 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) AS 'Name of Reviewer'
FROM Reviewer
WHERE rID IN (SELECT rID
			  FROM Rating
              WHERE ratingDate is null);

-- 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 AS 'Reviewer Name',
	   title AS 'Movie Title',
       stars AS 'Movie Stars Rating',
       ratingDate AS 'Date of Rating'
FROM Reviewer,Rating,Movie
WHERE Reviewer.rID=Rating.rID AND Movie.mID=Rating.mID
ORDER BY name, title, stars;

-- 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 AS 'Name of Reviewer', title AS 'Movie Title'
FROM Reviewer, Movie, Rating rt1, Rating rt2
WHERE (rt1.mID=Movie.mID)
  AND (Reviewer.rID=rt1.rID)
  AND (rt1.rID = rt2.rID)
  AND (rt2.mID = Movie.mID)
  AND (rt1.stars < rt2.stars)
  AND (rt1.ratingDate < rt2.ratingDate);

-- 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.
SELECT title,
MAX(stars)
FROM Movie, Rating
WHERE Movie.mID=Rating.mID
GROUP BY(Rating.mID)
ORDER BY(title);

-- 8.For each movie, return the title and the 'rating spread', 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 spread
FROM Movie, Rating
WHERE (Movie.mID=Rating.mID)
GROUP BY (title)
ORDER BY (spread) DESC;

-- 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
  Avg(CASE WHEN m.Year < 1980 THEN a.stars ELSE Null End) -
  Avg(CASE WHEN m.Year >= 1980 THEN a.stars ELSE Null End)
FROM (SELECT mID,
      AVG(stars) stars
      FROM rating
      GROUP BY mid) a INNER JOIN movie m ON m.mid = a.mid;

-- 10.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)
WHERE movie.mid
IN(SELECT rating.mid
   FROM rating
   GROUP BY mID
   HAVING avg(Stars) >= 4);