SELECT SINGLE b~lifnr INTO itab-lifnr   

     FROM mara AS a
     INNER JOIN eina AS b
        ON a~matnr = b~matnr
     INNER JOIN eine AS c
        ON b~infnr = c~infnr
     WHERE a~matnr = itab-idnrk
       AND c~werks = itab-werks
       AND c~ekorg =        =>1)

1)부분에서 c~ekorg를 가져와야 할때 처리를 어떻게 해야할지..