I ran the following query to UNION the result of two joins over the below 4 tables:
SELECT member_CROWD.worker_Id, member_CROWD.Unreliable, Answer_CROWD.qId, Answer_CROWD.answer FROM member_CROWD JOIN `Answer_CROWD` ON member_CROWD.worker_Id = Answer_CROWD.worker_Id WHERE member_CROWD.Unreliable = '0' AND Answer_CROWD.qId = 'q8' GROUP BY Answer_CROWD.answer UNION SELECT member.mem_id, member.Unreliable, Answer.qId, Answer.answer FROM member JOIN `Answer` ON member.mem_id = Answer.userId WHERE member.Unreliable = '0' AND Answer.qId = 'q8' GROUP BY Answer.answer
This is because I have two experiments to collect data; one is through asking my friends to fill my survey (data stored in member and Answer tables), and the other one is through Crowdsourcing (data stored in member_CROWD and Answer_CROWD).
Now the problem is that, I would like to know for example "Unique Number of Movies selected by users", but from all users (friends and also Crowd). The query above could UNION the two join results, BUT still answers are not unique (because they are unique ONLY in each join result).
Could someone help me know how to get Unique #of movies in the whole experiment?