How to build what a parent child record looked like from audit history

Question

I've got a simple parent child relationship (eg DEPT/EMP) and I have audit triggers on the 2 tables that log any changes. The 2 tables are seen by the User as 1 entity, so if an EMP record changes, that is essentially a DEPT change. I want to show a record where the info shown is correct at that particular point in time.
Now for a very crude example to illustrate...
So, says it's 9:00 and we have:
Dept 1=Sales
Emp 1=Clark
Emp 2=Smith
Now we change Emp 1 at 9:01 to Smythe
Next we change Dept 2 at 9:02 to Sales UK
Next we add Emp 3=Jones at 9:04
Next we change Emp1 at 9:05 to Clarke
So now if the User looks at the history of Dept 1 they will see it has changed at the following times:
9:01 (emp change)
9:02 (dept change)
9:04 (emp change)
9:05 (emp change)
even though the actual Dept table was only changed once.
This part is easy enough to extract but the next part I'm struggling to get my head around (must be Friday afternoon!).
The User wants to be able to view what the "Dept" looked like at the time of the change. So we would get the following results:
9:00 Dept 1=Sales, Emp 1=Clark, Emp 2=Smith (as per original data)
9:01 Dept 1=Sales, Emp 1=Clark, Emp 2=Smythe
9:02 Dept 1=Sales UK, Emp 1=Clark, Emp 2=Smythe
9:04 Dept 1=Sales UK, Emp 1=Clark, Emp 2=Smythe, Emp 3=Jones
9:05 Dept 1=Sales UK, Emp 1=Clarke, Emp 2=Smythe, Emp 3=Jones
I'm trying to write a bit of SQL to do this but the tricky bit comes in due to having 2 different tables that have triggered the change to a "DEPT". I see the output as being as many rows as there are children, so the raw output for the above summary would be along the lines of:
9:00, Dept 1=Sales, Emp 1=Clark
9:00, Dept 1=Sales, Emp 2=Smith
9:01, Dept 1=Sales, Emp 1=Clark
9:01, Dept 1=Sales, Emp 2=Smythe
9:02, Dept 1=Sales UK, Emp 1=Clark
9:02, Dept 1=Sales UK, Emp 2=Smythe
9:04, Dept 1=Sales UK, Emp 1=Clark
9:04, Dept 1=Sales UK, Emp 2=Smythe
9:04, Dept 1=Sales UK, Emp 3=Jones
9:05, Dept 1=Sales UK, Emp 1=Clarke
9:05, Dept 1=Sales UK, Emp 2=Smythe
9:05, Dept 1=Sales UK, Emp 3=Jones
Any help appreciated!!
An alternative to all this is to make my trigger on each table populate this info (ie write whatever is currently in place) into a table structured as I have mentioned above (so Dept i denormalised) but that looks to be a bit messy.

Answer 1

Two tables, Dept and Emp. Both have audit triggers inserting into it's own audit table.
create or replace table DEPT(
dept_no number,
dept_name varchar2(50),
dept_city varchar2(50));
create or replace table EMP(
emp_no number,
emp_surname varchar2(100),
emp_firstname varchar2(50),
emp_dept_no number);dept_no pk of DEPT
emp_no pk of EMP
emp_dept_no FK from EMP to DEPT.dept_no
create or replace table DEPT_AUDIT(
dept_no number,
dept_name varchar2(50),
dept_city varchar2(50),
audit_date_time date);
create or replace table EMP_AUDIT(
emp_no number,
emp_surname varchar2(100),
emp_firstname varchar2(50),
emp_dept_no number,
audit_date_time date)
create or replace trigger dept_audit
after insert or update
on dept for each row
begin
  insert into dept_audit(dept_no, dept_name, dept_city, audit_date_time)
  values(:NEW.dept_no, :NEW.dept_name, :NEW.dept_city, sysdate);
end;
create or replace trigger emp_audit
after insert or update
on emp for each row
begin
  insert into emp_audit(emp_no, emp_surname, emp_firstname, emp_dept_no, audit_date_time)
  values(:NEW.emp_no, :NEW.emp_surname, :NEW.emp_firstname, :NEW.emp_dept_no, sysdate);
end;My above example (ignoring that the columns don't match up but hopefully you get the drift) would end up with the following results in the 2 audit tables:
DEPT_AUDIT
9:00 Dept 1=Sales (insert)
9:02 Dept 1=Sales UK (update)
EMP_AUDIT
9:00 Emp 1=Clark (insert)
9:00 Emp 2=Smith (insert)
9:01 Emp 2=Smythe (update)
9:04 Emp 3=Jones (insert)
9:05 Emp 1=Clarke (update)
As I said originally, I want to get a view of what the "DEPT" looked like at a particular time and to do this I need to take into account the EMP changes for the DEPT which is why my results would be as follows:
9:00 Dept 1=Sales, Emp 1=Clark, Emp 2=Smith
9:01 Dept 1=Sales, Emp 1=Clark, Emp 2=Smythe
9:02 Dept 1=Sales UK, Emp 1=Clark, Emp 2=Smythe
9:04 Dept 1=Sales UK, Emp 1=Clark, Emp 2=Smythe, Emp 3=Jones
9:05 Dept 1=Sales UK, Emp 1=Clarke, Emp 2=Smythe, Emp 3=Jones
Though what I really want is the rows that make it up like:
9:00, Dept 1=Sales, Emp 1=Clark
9:00, Dept 1=Sales, Emp 2=Smith
9:01, Dept 1=Sales, Emp 1=Clark
9:01, Dept 1=Sales, Emp 2=Smythe
9:02, Dept 1=Sales UK, Emp 1=Clark
9:02, Dept 1=Sales UK, Emp 2=Smythe
9:04, Dept 1=Sales UK, Emp 1=Clark
9:04, Dept 1=Sales UK, Emp 2=Smythe
9:04, Dept 1=Sales UK, Emp 3=Jones
9:05, Dept 1=Sales UK, Emp 1=Clarke
9:05, Dept 1=Sales UK, Emp 2=Smythe
9:05, Dept 1=Sales UK, Emp 3=Jones
Hope that is a bit clearer.
thanks for taking time to look.