select
    CASE strftime('%w',SALES_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 WEEK
FROM SALES;