Question

Let say, I’ve a table in my database like this be it in POSTGRESQL or MYSQL :-

video_clip_name | bad | so_so | good|
video 1         | 20  | 13    | 3   |
video 2         | 12  | 20    | 33  |
video 3         | 40  | 34    | 33  |
video 4         | 20  | 23    | 13  |
video 5         | 20  | 13    | 37  |

I want to determine which video is rated as bad or so_so or good based on highest score after comparison is made between the three column (bad,so_so and good). Let say, video 1 has bad rating which is higher than the other two columns..this mean that video 1 has been rated as bad.

So my question is how to write such SQL statement in POSTGRESQL/MYSQL to output the overall rating for each video based on comparison between the three columns’ value?

thank you

Answer 1

Here is another way using CASE expression. I use SQL Server and not MySQL or PostGreSQL but I think this ANSI SQL compliant. The sample data and output uses various values. However, it they are all equal it currently will pick the rating in the order bad, *so_so* and good.

Script:

CREATE TABLE dbo.VideoRatings 
(
        video_clip_name VARCHAR(10) NOT NULL
    ,   bad             INT         NOT NULL
    ,   so_so           INT         NOT NULL
    ,   good            INT         NOT NULL
);

INSERT INTO  dbo.VideoRatings (video_clip_name, bad, so_so, good) VALUES
    ('video a', 1, 2, 3),
    ('video b', 2, 3, 1),
    ('video c', 3, 2, 1),
    ('video d', 2, 1, 1),
    ('video e', 1, 2, 2),
    ('video f', 1, 1, 2),
    ('video g', 2, 2, 2);

SELECT  video_clip_name
    ,   CASE 
            WHEN bad    >= so_so    AND bad     >= good     THEN 'bad'
            WHEN so_so  >= bad      AND so_so   >= good     THEN 'so_so'
            WHEN good   >= bad      AND good    >= so_so    THEN 'good'
        END AS Rating
FROM    dbo.VideoRatings;

Output:

video_clip_name rating
--------------- ------
video a         good
video b         so_so
video c         bad
video d         bad
video e         so_so
video f         good
video g         bad