Instead of Trigger Problems

Question

Good morning and thanks in advance for the help.  I'm new to oracle and sql in general, so bear with me if my create statements are wrong.  I am using Oracle 11g.
I am trying to create a trigger to do an update on a timesheet view in APEX.  The view draws from the assignment table and needs to store the data in the timesheet table.
CREATE TABLE assignment (
   assignment_id   number
   employee_id   number
   project_id   number)
CREATE TABLE timesheet (
   timesheet_id  number
   assignment_id  number
   week_start_date  date
   hours   number)
INSERT ALL
  INTO assignment (employee_id, project_id) VALUES (1, 1)
  INTO assignment (employee_id, project_id) VALUES (1, 2)
  INTO assignment (employee_id, project_id) VALUES (2, 1)
  INTO assignment (employee_id, project_id) VALUES (3, 2)
CREATE OR REPLACE FOR VIEW timesheet_view AS
SELECT *
FROM (SELECT A.assignment_id, project_id, employee_id, week_start_date, hours
      FROM timesheet T
      RIGHT OUTER JOIN assignment A
        ON T.assignment_id = A.assignment_id)
PIVOT (MAX(hours) FOR week_start_date IN (to_date('06/03/2013', 'MM/DD/YYYY') AS "06/03/2013",
to_date('06/10/2013', 'MM/DD/YYYY') AS "06/10/2013",
to_date('06/17/2013', 'MM/DD/YYYY') AS "06/17/2013",
to_date('06/24/2013', 'MM/DD/YYYY') AS "06/24/2013")
The view has many more columns since this needs to track weeks until they decide to stop using the app.
The view thus looks like this:
assignment_id  project_id  employee_id  06/03/2013  06/10/2013  06/17/2013  06/24/2013
1                      1                1                 25               15              15              15
2                      2                1                 15               25              25              -
3                      1                2                 40               40              40              40
4                      2                3                 40               -                40              -
So my question is, how do I create a trigger to insert into the timesheet table? I know how to create an instead of trigger, but what I don't know how to do is reference the column names for the date and then take the data that has been updated in each and store that in the timesheet table with the column name going in the week_start_date column and the value from the row at that column going into the hours column.  I'd love to be able to do it dynamically since adding a line to the trigger for every single date would be quite unruly.
Any help is greatly appreciated.

Answer 1

Yuck.  But you are hardcoding dates as columns into the view, so you'll have to change the view sometime anyway?  Could you not generate columns based on the MODEL clause?
Alternatively, have you considered adding a hidden (from the front end) column (weekno) for each date column to your view, but hiding it; in that column you could hardcode the date for the following column?
assignment_id  project_id  employee_id  week1dt         06/03/2013 week2dt          week3dt       06/10/2013  etc.
1                      1                1                06/10/2013    125             06/17/2013      06/10/2013    15           
edit: I was just wondering about an alternative: if you could prepend the week date (eg "06/03/2013") to the hours data for the row/column (e.g. "06/03/2013,40") then substring the hours (split on ",") in the APEX view, but you would have the weekdate to be able to use in your table update.  Just a thought; I've no experience with APEX.