WITH RECURSIVE
    DATES(REGIST_DATE) AS (
        VALUES ("2022-08-01")
        UNION ALL
            SELECT DATE(REGIST_DATE, "+1 DAY") FROM DATES WHERE REGIST_DATE < "2022-08-31"
    )
    
SELECT REGIST_DATE,
    CASE STRFTIME('%w', REGIST_DATE)
        WHEN "0" THEN "日"
        WHEN "1" THEN "月"
        WHEN "2" THEN "火"
        WHEN "3" THEN "水"
        WHEN "4" THEN "木"
        WHEN "5" THEN "金"
        WHEN "6" THEN "土"
    END AS WK,
    COUNT(USER_CODE) AS TOTAL
FROM DATES
    LEFT OUTER JOIN (SELECT * FROM USERS WHERE VALID_FLG = "1") AS U
        ON REGIST_DATE = DATE(U.CONFIRMED_AT)
GROUP BY REGIST_DATE