s/answers vs comment ไม่จำเป็นต้องใช้ตารางทั้งหมด
s/answers vs comments.It is not neccessary to use all the tables.
 ReviewTaskResultTypes:  Id [ number]  Name [ text]  Description [ text] 
SELECT t1.Count_1 AS "Number of questions and answers", t2.Count_2 AS "Number of comments" FROM (SELECT COUNT(1) AS Count_1 FROM Posts WHERE CreationDate <= '2017-09-30') AS t1, (SELECT COUNT(1) AS Count_2 FROM Comments WHERE CreationDate <= '2017-09-30') AS t2