SELECT DATE(CONFIRMED_AT) AS REGIST_DATE, SUBSTR('日月火水木金土', strftime("%w", CONFIRMED_AT, 'localtime')+1, 1) as WK, 
    CASE COUNT(*) WHEN NULL THEN 0
    ELSE COUNT(*) END
    AS TOTAL
FROM USERS
WHERE CONFIRMED_AT >= "2022-08-01" AND CONFIRMED_AT < "2022-09-01" 
    AND VALID_FLG = "1"
GROUP BY REGIST_DATE