SQL & PL/SQL :: UPDATE Multiple Fields Without Where Exist

I'm updating a big table with an other one (see topic

[URL]........

I was wondering if I could do it without using the WHERE EXISTS condition. Let me explain better:

create table TEST
(
ENT_SIG VARCHAR2(10),
EMP_ID VARCHAR2(10),
DATE_START DATE,
DATE_END DATE
);

create table TEST2
(
ENT_SIG VARCHAR2(10),
EMP_ID VARCHAR2(10),
DATE_START DATE,
DATE_END DATE
);

insert into TEST (ENT_SIG, EMP_ID, DATE_START, DATE_END)
values ('014', '120', TO_DATE('20080101','YYYYMMDD'), TO_DATE('20080131','YYYYMMDD'));
insert into TEST (ENT_SIG, EMP_ID, DATE_START, DATE_END)
values ('014', '121', TO_DATE('20080201','YYYYMMDD'), TO_DATE('20080228','YYYYMMDD'));
[code].....

I'm asking if there's a way to do this:

update test a
set (date_Start, date_end) = (select date_start, date_end
from test2 b
where b.emp_id = a.emp_id
[code].......

Without using the WHERE EXISTS. I don't want to make two accesses to table2, I would like instead to do something like "If subquery returns a row, use it, else keep what you have in destination table".

Is there a way to do it without entering test2 twice?