mysql select when matching multiple rows

Question

I have a project where I need to select only the users that answered to some questions in a certain way (based on a filter).

The filter table (filter) looks like this

   question |   answer  

   Q1       |    A  
   Q2       |    B 

The user table (answers) looks like this

user | question | answer  

  1  |    Q1    |    A  
  1  |    Q2    |    D  
  2  |    Q1    |    A  
  2  |    Q2    |    B 

How can I select from the user table only the user(s) that match the filter?
I tried

"SELECT user FROM answers WHERE (question = Q1 AND answer = A) 
             AND (question = Q2 AND answer = B)" 

and it doesn't work -- I get an empty result. Thank you.

Answer 1

In your query you are asking to get data which is not present. You are trying to get that user which has both the combination.

Try this

SELECT user FROM answers WHERE (question = 'Q1' AND answer = 'A') 
         OR (question = 'Q2' AND answer = 'B') 

Answer 2

try this

select answers.user
from filter, answers
where filter.question=answers.question and filter.answer=answers.answer
group by answers.user having count(answers.question)=2

or

select user
from answers
where user not in 
(select distinct a.user from answers a, filter f 
where a.question=f.question and a.answer!=f.answer)