SQL exercises on movie Database: Find the reviewer name, movie title, and stars for those movies which reviewed by a reviewer and must be rated
9. From the following tables, write a SQL query to find movies that have been reviewed by a reviewer and received a rating. Sort the result-set in ascending order by reviewer name, movie title, review Stars. Return reviewer name, movie title, review Stars.
Sample table: reviewerrev_id | rev_name --------+-------------------------------- 9001 | Righty Sock 9002 | Jack Malvern 9003 | Flagrant Baronessa 9004 | Alec Shaw 9005 | 9006 | Victor Woeltjen 9007 | Simon Wright 9008 | Neal Wruck 9009 | Paul Monks 9010 | Mike Salvati 9011 | 9012 | Wesley S. Walker 9013 | Sasha Goldshtein 9014 | Josh Cates 9015 | Krug Stillo 9016 | Scott LeBrun 9017 | Hannah Steele 9018 | Vincent Cadena 9019 | Brandt Sponseller 9020 | Richard AdamsSample table: rating
mov_id | rev_id | rev_stars | num_o_ratings
--------+--------+-----------+---------------
901 | 9001 | 8.40 | 263575
902 | 9002 | 7.90 | 20207
903 | 9003 | 8.30 | 202778
906 | 9005 | 8.20 | 484746
924 | 9006 | 7.30 |
908 | 9007 | 8.60 | 779489
909 | 9008 | | 227235
910 | 9009 | 3.00 | 195961
911 | 9010 | 8.10 | 203875
912 | 9011 | 8.40 |
914 | 9013 | 7.00 | 862618
915 | 9001 | 7.70 | 830095
916 | 9014 | 4.00 | 642132
925 | 9015 | 7.70 | 81328
918 | 9016 | | 580301
920 | 9017 | 8.10 | 609451
921 | 9018 | 8.00 | 667758
922 | 9019 | 8.40 | 511613
923 | 9020 | 6.70 | 13091
Sample table: movie
mov_id | mov_title | mov_year | mov_time | mov_lang | mov_dt_rel | mov_rel_country
--------+----------------------------------------------------+----------+----------+-----------------+------------+-----------------
901 | Vertigo | 1958 | 128 | English | 1958-08-24 | UK
902 | The Innocents | 1961 | 100 | English | 1962-02-19 | SW
903 | Lawrence of Arabia | 1962 | 216 | English | 1962-12-11 | UK
904 | The Deer Hunter | 1978 | 183 | English | 1979-03-08 | UK
905 | Amadeus | 1984 | 160 | English | 1985-01-07 | UK
906 | Blade Runner | 1982 | 117 | English | 1982-09-09 | UK
907 | Eyes Wide Shut | 1999 | 159 | English | | UK
908 | The Usual Suspects | 1995 | 106 | English | 1995-08-25 | UK
909 | Chinatown | 1974 | 130 | English | 1974-08-09 | UK
910 | Boogie Nights | 1997 | 155 | English | 1998-02-16 | UK
911 | Annie Hall | 1977 | 93 | English | 1977-04-20 | USA
912 | Princess Mononoke | 1997 | 134 | Japanese | 2001-10-19 | UK
913 | The Shawshank Redemption | 1994 | 142 | English | 1995-02-17 | UK
914 | American Beauty | 1999 | 122 | English | | UK
915 | Titanic | 1997 | 194 | English | 1998-01-23 | UK
916 | Good Will Hunting | 1997 | 126 | English | 1998-06-03 | UK
917 | Deliverance | 1972 | 109 | English | 1982-10-05 | UK
918 | Trainspotting | 1996 | 94 | English | 1996-02-23 | UK
919 | The Prestige | 2006 | 130 | English | 2006-11-10 | UK
920 | Donnie Darko | 2001 | 113 | English | | UK
921 | Slumdog Millionaire | 2008 | 120 | English | 2009-01-09 | UK
922 | Aliens | 1986 | 137 | English | 1986-08-29 | UK
923 | Beyond the Sea | 2004 | 118 | English | 2004-11-26 | UK
924 | Avatar | 2009 | 162 | English | 2009-12-17 | UK
926 | Seven Samurai | 1954 | 207 | Japanese | 1954-04-26 | JP
927 | Spirited Away | 2001 | 125 | Japanese | 2003-09-12 | UK
928 | Back to the Future | 1985 | 116 | English | 1985-12-04 | UK
925 | Braveheart | 1995 | 178 | English | 1995-09-08 | UK
Sample Solution:
-- Selecting reviewer name, movie title, and review stars
-- Using the 'reviewer', 'rating', and 'movie' tables
-- Joining tables based on rev_id and mov_id
SELECT rev_name, mov_title, rev_stars
FROM reviewer, rating, movie
WHERE reviewer.rev_id = rating.rev_id
AND movie.mov_id = rating.mov_id
-- Filtering out NULL values for rev_name and rev_stars
AND reviewer.rev_name IS NOT NULL
AND rating.rev_stars IS NOT NULL
-- Ordering the result set by rev_name, mov_title, and rev_stars
ORDER BY rev_name, mov_title, rev_stars;
Sample Output:
rev_name | mov_title | rev_stars
--------------------------------+----------------------------------------------------+-----------
Brandt Sponseller | Aliens | 8.40
Flagrant Baronessa | Lawrence of Arabia | 8.30
Hannah Steele | Donnie Darko | 8.10
Jack Malvern | The Innocents | 7.90
Josh Cates | Good Will Hunting | 4.00
Krug Stillo | Braveheart | 7.70
Mike Salvati | Annie Hall | 8.10
Paul Monks | Boogie Nights | 3.00
Richard Adams | Beyond the Sea | 6.70
Righty Sock | Titanic | 7.70
Righty Sock | Vertigo | 8.40
Sasha Goldshtein | American Beauty | 7.00
Simon Wright | The Usual Suspects | 8.60
Victor Woeltjen | Avatar | 7.30
Vincent Cadena | Slumdog Millionaire | 8.00
(15 rows)
Code Explanation:
The said query in SQL that selects data from the tables reviewer, rating, and movie. As a result, it will retrieve the name of the reviewer, the title of the movie, as well as the number of stars that the reviewer has given in their rating.
The condition is specifies that the reviewer ID in the reviewer table must match the reviewer ID in the rating table, and the movie ID in the movie table must match the movie ID in the rating table. It also specifies that the reviewer name and rating stars must not be null.
The results are sorted in ascending order by reviewer name, movie title, and rating stars.
Alternative Solutions:
Using INNER JOIN:
SELECT r.rev_name, m.mov_title, ra.rev_stars
FROM reviewer r
JOIN rating ra ON r.rev_id = ra.rev_id
JOIN movie m ON m.mov_id = ra.mov_id
WHERE r.rev_name IS NOT NULL AND ra.rev_stars IS NOT NULL
ORDER BY r.rev_name, m.mov_title, ra.rev_stars;
Explanation:
This solution uses the modern INNER JOIN syntax to combine the reviewer, rating, and movie tables based on their respective IDs. It includes conditions to ensure that rev_name and rev_stars are not NULL. The result set is ordered accordingly.
Using INNER JOIN with ON Clause:
SELECT r.rev_name, m.mov_title, ra.rev_stars
FROM reviewer r
INNER JOIN rating ra ON r.rev_id = ra.rev_id
INNER JOIN movie m ON m.mov_id = ra.mov_id
WHERE r.rev_name IS NOT NULL AND ra.rev_stars IS NOT NULL
ORDER BY r.rev_name, m.mov_title, ra.rev_stars;
Explanation:
This query also uses the INNER JOIN syntax but explicitly specifies the join conditions using the ON clause. It achieves the same result as the first solution.
Using INNER JOIN with Subqueries:
SELECT r.rev_name, m.mov_title, ra.rev_stars
FROM (
SELECT *
FROM reviewer
WHERE rev_name IS NOT NULL
) r
JOIN (
SELECT *
FROM rating
WHERE rev_stars IS NOT NULL
) ra ON r.rev_id = ra.rev_id
JOIN movie m ON m.mov_id = ra.mov_id
ORDER BY r.rev_name, m.mov_title, ra.rev_stars;
Explanation:
This query uses subqueries to filter the reviewer and rating tables for non-null values before performing the joins. The result is then joined with the movie table, and the final result set is ordered accordingly.
Relational Algebra Expression:
Relational Algebra Tree:
Practice Online
Query Visualization:
Duration:
Rows:
Cost:
Have another way to solve this solution? Contribute your code (and comments) through Disqus.
Previous: From the following tables, write a SQL query to find those reviewers who have rated nothing for some movies. Return reviewer name.
Next: From the following table, write a SQL query to find those reviewers who rated more than one movie. Group the result set on reviewer’s name, movie title. Return reviewer’s name, movie title.
What is the difficulty level of this exercise?
Test your Programming skills with w3resource's quiz.