CREATE TABLE IMPORT_TAB ( IDNR VARCHAR2(10) , PIECES NUMBER )
ALTER TABLE IMPORT_TAB ADD (
	CONSTRAINT IMPORT_TAB_PK PRIMARY KEY ( IDNR ));

INSERT INTO IMPORT_TAB ( IDNR , PIECES ) VALUES ( '012.34' , 5 );
INSERT INTO IMPORT_TAB ( IDNR , PIECES ) VALUES ( '012.34A' , 3 );
INSERT INTO IMPORT_TAB ( IDNR , PIECES ) VALUES ( '012.34B' , 1 );
INSERT INTO IMPORT_TAB ( IDNR , PIECES ) VALUES ( '056.78B' , 3 );
INSERT INTO IMPORT_TAB ( IDNR , PIECES ) VALUES ( '789.34A' , 2 );
INSERT INTO IMPORT_TAB ( IDNR , PIECES ) VALUES ( '789.34C' , 5 );
/

UPDATE TARGET_TAB SET PIECES1 = 9 WHERE IDNR = '012.34';  -- where 9 is the sum of all '012.34%' in IMPORT_TAB
UPDATE TARGET_TAB SET PIECES1 = 3 WHERE IDNR = '056.78';
UPDATE TARGET_TAB SET PIECES1 = 7 WHERE IDNR = '789.34';

TYPE kdmenge_tab IS TABLE OF NUMBER   
    INDEX BY VARCHAR2( 10 );
kdmenge     kdmenge_tab;

l_idnr TARGET_TAB.IDNR%TYPE;

CURSOR c1 IS
SELECT IDNR, PIECES FROM IMPORT_TAB ORDER BY IDNR;

counter NUMBER;

BEGIN
counter := 0 ;

-- populate collection
FOR rec in c1
LOOP
	counter := counter +1 ;
	l_idnr := REGEXP_REPLACE ( rec.IDNR , 'A|B|C|D|E' , '' ) ;
	
	IF ( kdmenge.EXISTS( l_idnr ) ) THEN
		kdmenge( l_idnr ) := kdmenge( l_idnr ) + rec.PIECES ;
	ELSE
		kdmenge( l_idnr ) := rec.PIECES ;
	END IF;

NULL;
END LOOP;

l_idnr := kdmnege.FIRST;
WHILE ( l_idnr IS NOT NULL ) 
LOOP
	UPDATE TARGET_TAB
	SET PIECES1 = kdmenge( l_idnr )
	WHERE TARGET_TAB.IDNR = l_idnr ;
	
	l_idnr := kdmenge.NEXT( l_idnr );
END LOOP;

UPDATE TARGET_TAB  T
SET PIECES1 = ( SELECT SUM(PIECES) FROM IMPORT_TAB I WHERE I.IDNR LIKE T.IDNR||'%' )
WHERE EXISTS ( SELECT NULL FROM IMPORT_TAB I WHERE I.IDNR LIKE T.IDNR||'%' )
/