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Asked: 2026-05-31T10:47:49+00:00

NOTE: I accidentally put another question’s sentence in here (massive apologies on my part),

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NOTE: I accidentally put another question’s sentence in here (massive apologies on my part), I have updated this post as of Wednesday 14th March at 23:21pm with the correct question.

I have spent a few hours trying to figure out this question without anyone’s help but have realised I have wasted too much productive time and should’ve asked someone sooner. I had a decent crack at this and have come so close but cannot get the final solution I need. What I am supposed to get is:

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.

This is the query I managed to get here:

SELECT reviewer.name, movie.title, rating.stars  
FROM (reviewer JOIN rating ON reviewer.rid = rating.rid)  
JOIN movie ON movie.mid = rating.mid  
GROUP BY reviewer.name 
HAVING COUNT(*) >= 2  
ORDER BY reviewer.name DESC

(I have a feeling there is a missing WHERE clause from the above query, but am not sure where to place it)

(From what I have learned, RIGHT and FULL OUTER JOINs are not currently supported in SQLite)

And here are the tables and data (in pictures)…

Movie

Reviewer

Rating

… And the DB code…

/* 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');

I have another relatively similar question like this, but if I get some help on this one I should be able to apply the patterns and techniques from this one to the next one.

Thanks in advance! 🙂

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1 Answer

  1. Editorial Team

    I have added an inner join with derived table that returns maximum stars per movie. Because of inner join between movies and ratings only movies with ratings will be retrieved. Join it back to main query to get maximum stars per movie.

    Note: you stated that you wish to order by movie title but your query orders by reviewer.

    SELECT reviewer.name, movie.title, rating.stars, maxStarsPerMovie.MaxStars
FROM (reviewer JOIN rating ON reviewer.rid = rating.rid)  
JOIN movie ON movie.mid = rating.mid  
join
(
   select movie.mid, max(rating.stars) MaxStars
   from movie
   inner join rating
      on movie.mid = rating.mid
   group by movie.mid
) maxStarsPerMovie
on movie.mid = maxStarsPerMovie.mid
ORDER BY reviewer.name DESC

    EDIT: requiremets changed. This query will return list of reviewers who changed their opinion at later date in favor of the movie. It does so by joining ratings for the second time adding two filters on stars and date to join.

    SELECT reviewer.name, movie.title, rating.ratingDate, rating.stars,
       newRating.ratingDate newRatingDate, newRating.Stars newRatingStars
FROM (reviewer JOIN rating ON reviewer.rid = rating.rid)  
JOIN movie ON movie.mid = rating.mid 
inner join rating newRating
     on newRating.mid = movie.mid
        and newRating.rid = reviewer.rid
        and newRating.ratingdate > rating.ratingdate
        and newRating.stars > rating.stars
ORDER BY reviewer.name, movie.title
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