query to find diff between two records - mysql

Question

I have following tables
movies
- id
details
- user_id
- movie_id
- rating
users
- id
detail belongs to user and movie
I want to find the the diff between the rating of two users say id 3,10
simply I want answer of this
sum(10-(user1.rating - user2.rating))
where rating is > 0
i.e both users should have given at-least non zero rating

Answer 1

select
d1.movie_id
, d1.rating as user1Rating
, d2.rating as user2Rating
, abs(d1.rating - d2.rating)
from
details d1
inner join details d2 on d1.movie_id = d2.movie_id
where d1.user_id = 1
and d2.user_id = 2
See it working live in an sqlfiddle.

Answer 2

CREATE TABLE ratings
( userId int, movieId int, rating int)
INSERT INTO ratings (userId, movieId, rating) VALUES
(3, 1, 5), (10, 1, 8),
(3, 2, 10), (10, 2, 3)
SELECT r1.movieId, (r1.rating - r2.rating) FROM ratings as r1
INNER JOIN ratings as r2 on r1.movieId = r2.movieId
WHERE r1.userId = 3 and r2.userId = 10

Answer 3

DECLARE #UserRating1 int
DECLARE #UserRating2 int
DECLARE #UserID1 int
DECLARE #UserID2 int
DECLARE #MovieID int
SET #MovieID = 99
SET #UserID1 = 3
SET #UserID2 = 10
SET #UserRating1 = (SELECT Rating FROM details WHERE movie_id = #MovieID AND user_id = #UserID1 AND Rating > 0)
SET #UserRating2 = (SELECT Rating FROM details WHERE movie_id = #MovieID AND user_id = #UserID2 AND Rating > 0)
PRINT #UserRating1 - #UserRating2

Answer 4

Update: I replace the syntax from MSSQL to MySql
You can check this on SQL Fiddle:
create table movies (id int);
insert into movies (id) values (1);
insert into movies (id) values (2);
insert into movies (id) values (3);
insert into movies (id) values (4);
insert into movies (id) values (5);
create table users (id int);
insert into users (id) values (1);
insert into users (id) values (2);
insert into users (id) values (3);
insert into users (id) values (4);
insert into users (id) values (5);
insert into users (id) values (10);
create table details (user_id int, movie_id int, rating int);
insert into details (user_id, movie_id, rating) values (3,1,1);
insert into details (user_id, movie_id, rating) values (3,2,2);
insert into details (user_id, movie_id, rating) values (3,3,3);
insert into details (user_id, movie_id, rating) values (3,4,1);
insert into details (user_id, movie_id, rating) values (3,5,4);
insert into details (user_id, movie_id, rating) values (10,1,3);
insert into details (user_id, movie_id, rating) values (10,2,1);
insert into details (user_id, movie_id, rating) values (10,3,2);
insert into details (user_id, movie_id, rating) values (10,4,1);
insert into details (user_id, movie_id, rating) values (10,5,5);
and
select
sum(10-(details1.rating - details2.rating))
from
movies
inner join details details1 on movies.id = details1.movie_id
inner join users user1 on details1.user_id = user1.id
inner join details details2 on movies.id = details2.movie_id
inner join users user2 on details2.user_id = user2.id
where
(user1.id=3)
and
(user2.id=10)
and
(details1.rating is not null) and (details1.rating > 0)
and
(details2.rating is not null) and (details2.rating > 0)