DELETE FROM
    ITEM
WHERE
    ITEM.STOCK_MANAGEMENT_TYPE = 1 AND
    (
        NOT EXISTS(
            SELECT
                STOCK.ITEM_CODE
            FROM
                STOCK
            WHERE
                STOCK.ITEM_CODE = ITEM.ITEM_CODE
        )
        OR
        (
            SELECT
                STOCK.ACTUAL_AMT
            FROM
                STOCK
            WHERE
                STOCK.ITEM_CODE = ITEM.ITEM_CODE AND
                (
                    STOCK.LAST_DELIVERY_DATE IS NULL OR
                    STOCK.LAST_DELIVERY_DATE <= DATE(STOCK.LAST_DELIVERY_DATE, '-6 months')
                )
            ORDER BY
                STOCK.LAST_DELIVERY_DATE DESC
            LIMIT 1
        ) = 0
    )
;