Q&A for scientific skepticism
--SELECT ROUND((SELECT DISTINCT COUNT(U.id) FROM USERS U --LEFT JOIN POSTS P --ON U.Id = P.OwnerUserId WHERE U.id >= -1 and P.Id is NULL) / (SELECT count(id) FROM USERS), 2) * 100 AS RESULT; WITH CTE1 AS ( SELECT DISTINCT COUNT(U.id) AS count_post FROM USERS U LEFT JOIN POSTS P ON U.Id = P.OwnerUserId WHERE U.id >= -1 and P.Id is NULL ), CTE2 AS ( SELECT count(id) AS count_nopost FROM USERS ) SELECT (100 * CTE1.count_post / CTE2.count_nopost) FROM CTE1, CTE2