DELETE FROM ITEM
WHERE ITEM_CODE NOT IN (SELECT ITEM_CODE FROM STOCK) 
    OR ITEM_CODE IN (SELECT ITEM_CODE 
                    FROM STOCK STOCKA
                    WHERE LAST_DELIVERY_DATE IS NOT NULL 
                        AND ACTUAL_AMT = 0 
                        AND LAST_DELIVERY_DATE = (SELECT MAX(LAST_DELIVERY_DATE) MAXDATE
                                                    FROM STOCK STOCKB
                                                    WHERE STOCKA.ITEM_CODE = STOCKB.ITEM_CODE
                                                        AND MAXDATE <= DATE('2023-06-01', '-6 months') 
                                                    GROUP BY ITEM_CODE)