Oracle SQL query to return 1 or 0 based on if value exists -

i have 2 table question , answer tables. question table has

id question_text 1  question1 2  question2 3  question3 

answer table

question_id answer_text answered_by 1           ans1        user1 1           ans2        user2 1           ans3        user3 2           ans4        user1 

i need find out questions answered already? desired outcome

id question_text answered 1  question1     true/1 2  question2     true/1 3  question3     false/0 

i have written below query find whether question answered using exists. need answered value true/false , want fine tune query checks first occurrence in answer table , value true/false, instead of running through thousands of value in answer table.

select *  questions   exists (select *                 answers b                 a.question_id = b.question_id); 

a simple left join do:

select  q.*,          case when a.question_id null 0 else 1 end answered question q left join ( select distinct question_id             answer)     on q.id = a.question_id;