/*SELECT *
FROM ITEM A
where
    not exists(
        SELECT * from STOCK B WHERE A.ITEM_CODE=B.ITEM_CODE
        )
    or exists(
        SELECT * from (
            SELECT
                MAX(LAST_DELIVERY_DATE) MDATE,
                SUM(ACTUAL_AMT) mamt,
                ITEM_CODE
            FROM
                STOCK
            GROUP BY
                ITEM_CODE
            ) C 
        WHERE
            A.ITEM_CODE=C.ITEM_CODE
        AND DATE(C.MDATE) <= DATE('now','-6 months')
        AND mamt=0)
*/

delete FROM ITEM
where
    not exists(
        SELECT * from STOCK B WHERE ITEM.ITEM_CODE=B.ITEM_CODE
        )
    or exists(
        SELECT * from (
            SELECT
                MAX(LAST_DELIVERY_DATE) MDATE,
                SUM(ACTUAL_AMT) mamt,
                ITEM_CODE
            FROM
                STOCK
            GROUP BY
                ITEM_CODE
            ) C 
        WHERE
            ITEM.ITEM_CODE=C.ITEM_CODE
        AND DATE(C.MDATE) <= DATE('now','-6 months')
        AND mamt=0)