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

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)