How can i write this query in MySql? -


i have table: 

    question_id | user_id | answer | weight         213     |   22    |   25   |   50         213     |   106   |   75   |   50         216     |   22    |   100  |   50         216     |   106   |   0    |   50

i want write mysql query calculate, 2 specified user_id's:

user1's weight * (user1's answer - user2's answer)

and sum values question_id's. so, example above, if user1's id 22 , user2's id 106:

50*(25-75)+50*(100-0)=2500

you can self join:

select sum(u1.weight * (u1.answer - u2.answer)) total table u1 join table u2 on u2.question_id = u1.question_id u1.user_id = 22 , u2.user_id = 106

make sure column types not "unsigned", otherwise, you'll need cast values signed.


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