Atualizar tabela de outra tabela no oracle

DECLARE
  l_date DATE:=TO_DATE('01/04/2017','DD/MM/YYYY');
BEGIN
  LOOP
    EXECUTE IMMEDIATE 'MERGE INTO EMPSHIFT E
USING SCHEDULEEMPLOYEES S
ON (S.EMPLOYEEID=E.EMPLOYEEID AND S.DAYDATE=TO_DATE('''||TO_CHAR(l_date)||''',''DD/MM/YYYY''))
WHEN MATCHED 
THEN UPDATE SET E."'||TO_CHAR(l_date)||'"=S.SHIFT';
    l_date:=l_date+1;
    EXIT
  WHEN l_date>TO_DATE('30/04/2017','DD/MM/YYYY');
  END LOOP;
END;