合并2个表并比较SQL / PHP的不同结果

I'm really struggling here to do this. I've looked online but I just don't understand what other people are doing and how it would work for my situation.

I have a questions table with questions (Columns: question_id, question, answer1, answer2, questioner_id), then I have a table (questions_answered) with rows of who answered what question. (Columns: user_id and question_id)

I need to grab questions for the user but make sure that I don't pick questions that the user has already answered by comparing the user_id and question_id.

I'm racking my head over how to do this. I've tried to do two sets of queries and comparing the arrays to no avail.

I'm now trying to do it in 1 query but I'm just so unsure of how.

Please may anyone help me?

If you need any more information just say

Kindest Regards

Try this with subquery

SELECT * FROM questions  q
WHERE q.question_id NOT IN
(SELECT qa.question_id FROM questions_answered qa WHERE qa.user_id ='1')

or use NOT EXISTS

SELECT * FROM questions  q
WHERE   NOT EXISTS 
(SELECT * FROM questions_answered qa WHERE qa.user_id ='1')

or

SELECT * FROM questions  q
WHERE   NOT EXISTS 
(SELECT * FROM questions_answered qa WHERE qa.question_id =q.question_id   AND qa.user_id ='1')

Subqueries with EXISTS or NOT EXISTS