WITH DATE_8 AS ( 
SELECT
    '2022-08-01' AS REGIST_DATE 
UNION ALL 
SELECT
    DATE(REGIST_DATE, '+1 days')
FROM
    DATE_8 
WHERE
    REGIST_DATE < '2022-08-31'
),
tbl_1 AS (
SELECT
    STRFTIME('%Y-%m-%d', CONFIRMED_AT) AS REGIST_DATE
    ,STRFTIME('%m', CREATED_AT) AS CREATED_MONTH
    ,COUNT(USER_CODE) AS TOTAL
FROM
    USERS
WHERE   
    VALID_FLG='1'
    AND CREATED_MONTH = '08'
    AND REGIST_DATE IS NOT NULL
GROUP BY
    REGIST_DATE  
)
SELECT 
    DATE_8.REGIST_DATE
    ,CASE STRFTIME('%w', DATE_8.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
    ,IFNULL(TOTAL,0) AS TOTAL
FROM DATE_8
LEFT JOIN
    tbl_1
ON  
    DATE_8.REGIST_DATE = tbl_1.REGIST_DATE
;