select
    strftime('%Y-%m', SALES_DATE) AS YEAR_MONTH,
    SUM(SALES_AMT) AS MONTH_AMT,
    (select SUM(SALES_AMT) FROM SALES t2
     where UPDATED_NO is NULL and SALES_DATE >= '2023-01-01' and SALES_DATE <= '2023-12-31' and strftime('%Y-%m', t2.SALES_DATE) <= strftime('%Y-%m', t1.SALES_DATE)) AS CUML_AMT
from SALES t1
where UPDATED_NO is NULL and SALES_DATE >= '2023-01-01' and SALES_DATE <= '2023-12-31'
group by strftime('%Y-%m', SALES_DATE)