How to order by from third table (related to Max(), join) - mysql

Question

Let me explain the question with the following example: (long but easy to understand)
This is how my MySQL database looks like:
table name: general_info
Movie_ID movie_title
1 Iron Man
2 Superman
3 Batman
table name: cast
Movie_ID Cast_Name
1 Robert Downey Jr.
1 Gwyneth Paltrow
2 Henry Cavill
2 Amy Adams
3 Christian Bale
3 Heath Ledger
Table name production_companies
Movie_ID Production_name
1 Marvel
1 Paramount
2 Legendary Pictures
2 DC Entertainment
3 Snycopy
table name user_cast_preference
user_id user_cast_name user_cast_rating
1 Robert Downey Jr. 95
1 Gwyneth Paltrow 45
1 Christian Bale 80
1 Heath Ledger 90
table name user_production_preference
user_id user_production_name user_production_rating
1 Marvel 85
1 Paraamount 70
1 Syncopy 65
Now, I am able to fetch all movies that are in user's preferred cast + preferred production company, using this query
select general_info.movie_id,movie_title from general_info
inner join cast on general_info.movie_id = cast.movie_id
inner join production_companies on general_info.movie_id = production_companies.movie_id
where cast.cast_name in (select user_cast_name from user_cast_preference)
or production_companies.production_companie_name in (select user_production_name from user_production_preference)
group by movie_title
Current Result:
movie_id moive_title
3 Batman
1 Iron Man
Only batman and Ironman got fetched because at least one of the actor or production company was involved in it (which is also in user's preferred list)
Till now everything is just fine. But I want to do this:
I want to order movies by this algorithem.
I will compare all fetched movies with the given rating in my tables and order them by Top to bottom.
In my case, let's compare Batman and Iron Man.
This is how, I decided to compare.
Take the top rated cast from Ironman + Top rated production company from iron man
Take the top rated cast from Batman + Top rated production company from batman
that is:
95 (iron man) + 85 (marvel) = 180
90 (heath ledger) + 65 (syncopy) = 155
Now Iron man has more rating than Batman, so expected result will be:
movie_id moive_title total_rating
1 Iron Man 180
3 BatMan 155
I hope, I made myself clear.

Answer 1

You want all movies where the user either have an actor or a company (or both) in their preferences. Then you want to sort by the sum of top preferences.
I'd look up the maximum points of user-rated casts and maximum points of user-rated companies per movie first and then outer join these aggregation results to the movie table:
select gi.*
from general_info
left join
(
select c.movie_id, max(ucp.user_cast_rating) as points
from cast c
join user_cast_preference ucp on ucp.user_cast_name = c.cast_name
where ucp.user_id = 1
group by c.movie_id
) p1 on p1.movie_id = gi.movie_id
left join
(
select pc.movie_id, max(upp.user_cast_rating) as points
from production_companies pc
join user_production_preference upp on upp.user_cast_name = pc.cast_name
where upp.user_id = 1
group by pc.movie_id
) p2 on p1.movie_id = gi.movie_id
where p1.points > 0 or p2.points > 0
order by coalesce(p1.points, 0) + coalesce(p2.points, 0) desc;

Answer 2

Not sure where you are getting "production_companies.production_companie_name" in your original code
SELECT general_info.Movie_ID,
general_info.movie_title,
MAX(user_cast_preference.user_cast_rating + user_production_preference.user_production_rating) AS total_rating
FROM ((((general_info
INNER JOIN CAST ON general_info.Movie_ID = cast.Movie_ID)
INNER JOIN production_companies ON cast.Movie_ID = production_companies.Movie_ID)
INNER JOIN user_production_preference ON production_companies.Production_name = user_production_preference.user_production_name)
INNER JOIN user_cast_preference ON cast.Cast_Name = user_cast_preference.user_cast_name)
GROUP BY movie_title
ORDER BY total_rating DESC;