bu şekilde çözdüm
xxxx ITM SET ITM.PRODUCERCODE=UNI.BARCODE FROM LG_004_ITEMS ITM , LG_004_UNITBARCODE UNI ,LG_004_ITMUNITA ITA
WHERE ITM.LOGICALREF=UNI.ITEMREF AND ITM.LOGICALREF=ITA.ITEMREF AND ITA.LOGICALREF=UNI.ITMUNITAREF AND ITA.LINENR=1 AND UNI.LINENR=1