| video_id | title   | duration |
|-------------------------------|
| 12       | title12 | 190      |
| 24       | title24 | 190      |
| 78       | title78 | 190      |
| 34       | title34 | 190      |
| 91       | title91 | 190      |
| 88       | title88 | 190      |

| video_category_id | name    |
|-----------------------------|
| 4                 | music   |
| 8                 | tv      |
| 5                 | black   |
| 2                 | politic |
| 1                 | movie   |
| 6                 | other   |

| video_id | video_category_id |
|------------------------------|
| 24       | 4                 |
| 24       | 5                 |
| 78       | 4                 |
| 78       | 5                 |
| 88       | 1                 |
| 91       | 4                 |
| 91       | 1                 |

| video_id |
|----------|
| 78       |
| 91       |
| 12       |
| 34       |
| 91       |

SELECT video_id, title, duration
FROM (
    (
     SELECT v.video_id, v.title, v.duration, 1 AS preferred
    FROM video_category_join vc
    JOIN video_category_join vc2 ON vc2.video_category_id = vc.video_category_id AND vc2.video_id <> vc.video_id
    JOIN video v ON v.video_id = vc2.video_id
    WHERE vc.video_id = 24
    GROUP BY vc2.video_id
    ORDER BY RAND()
    LIMIT 20
    )
    UNION
    (
    ...
    )
) AS t1
ORDER BY preferred
LIMIT 20