How Can I Use Triggers to Pre-Populate a Table

Question

I've given up on using collections, time to move on to plan B.
I'm working on building a training database and I have 3 tables, one which houses employee information (A), one which houses training courses (B) and a third what stores the results of completed training (C). What I'd like to do is store all possible combinations of A*B (M:M) in table C and throw a tabular form on table C to provide for mass updates.
This is easy enough if my employee base (A) and my training courses (B) weren't changing throughout the year. What I'd like to accomplish is to place a trigger on each table so that when it is updated the new record is copied to table C along with all combinations of the other table.
For example:
If I add a new employee A, a trigger on that table will run which takes the new employee and creates records in table C, with all possible combinations of courses in table B. (1:M)
or
If I add a new course B, a trigger on that table will run which takes the new course and creates records in table C, with all possible combinations of employees in table A. (M:1)
Let's just say the tables look like the following:
A
employee_num (PK)
employee_name
password
active
B
course_ID (PK)
course_name
Course_code
Course_hours
C
ID (PK)
employee_num (FK)
course_ID (FK)
approved_status
approved_by
date_taken
Does anyone have any pseudo code, links, sample applications, encouraging words I could leverage to get started?
Thanks much.

Answer 1

I've never created a trigger to do what your asking. I personally try to limit my use of triggers to surrogate keys.
That being said I have done something similar to your situation. If you are managing the employees and the courses in apex just make that page process create your new records in your other tables.
Ex. Add new employee
Declare
v_id number;
Begin
If creating
v_id := what ever your next employee_id
Issue your create on the employee table specifying v_id as the value of the employee_id
Create an insert from select for the "c" table something like:
Insert into c (employee_id,course_id)
Select v_id, course_id from b ;
End if;
End;
I would do something similar on the courses page to solve ex 2.