Select users with right answers only

Hi, all
Statistic page show all users answers, right and wrong.
I need to select winners only and use code bellow:

SELECT U.ID, count(QA.correct_count), sum(QA.correct_count)
FROM wp_users U, wp_wp_pro_quiz_statistic_ref QS, wp_wp_pro_quiz_statistic QA
WHERE U.ID = QS.user_id AND QS.statistic_ref_id = QA.statistic_ref_id and QS.quiz_id = 1 /* quiz ID */
group by U.ID
order by 3

Is it is right way?

PS winners -> Random.org -> winner ??

https://www.ads-software.com/plugins/wp-pro-quiz/