Questions on Master-Detail HTMLDB HOW-TO

Question

Hi all
I have created a 3 page application based on the master detail how-to given at http://www.oracle.com/technology/products/database/htmldb/howtos/index.html
Instead of DEPT and EMP tables I have PERSON and PERSON_ADDR tables. The PK of PERSON is the person_id and the PK of PERSON_ADDR is the person_id and addr_start_dt. Person_id column in PERSON_ADDR is obviously the FK to the master table PERSON(person_id).
At first I had problems trying to create the pages themselves because the wizard always hides the person_id column on all the forms(and I don't want that,even though it is a sequence number I still want people to see it) , it being the PK, then somehow I managed it to display the person_id by replacing the EDIT link with the person_id itself. Now if a person already has an address and I click on EDIT then it copies the person_id values and others to the next page and all looks good but when I try to create a new address it does it ?? (It should take across the person_id as well)
My PERSON report is on page 1, when I click edit against a person it takes me to page 2 where I can see+change all the person details plus I can see the person_addr details. When I click edit against a person address it takes me to page 3 and I can edit all the address details nicely copied to the new page but when I click CREATE on the page 2, then all the fields appear as NULL on page 3( all the fields but the person_id should be null here). How can I fix this ?
Also, for my person address I would like to validate the address dates , there should be no overlapping start and end dates for a person's address. How to do this ? I think I will need to create a function to which I pass the person id and the new start and end dates and this function returns error message,if any, or null. I had a play around with validation and I think I need to use "function returning error text", what should I put in the "validate expression 1" box then...just something like
begin
my_function(param_1,param_2)
end;
If yes, then what variables would store the new start date and new end date of an address.
Lastly, for every table do I have to user a sequence number or a trigger to define a primary key, what if the primary key is just a character code and I want the users to add it ?
Thanks a lot in advance !!

Answer 1

thanks Marc.
Yes you are right, I used the 1.5 viewlet. I will try the master-detail wizard now.
With the primary key problems, for things to work nicely in HTMLDB, do you suggest each and every tables should have a sequence number generated primary key ? We have some tables for various statuses like ACTIVE,CLOSED where these codes themselves are the primary keys, so you suggest making these codes unique keys but still have a sequence number PK ? Also when I want the users to enter the primary key themselves I will let them enter new ones but not update existing ones, so data entegrity is maintained.
I was able to work out how to create validations using "functions returning error text" but my problem is I need to be able to compare what the user has just updated/entered with the data that already exists in the table. I have a table called person_Address having columns like person_id, start_dt,end_dt and various other fields. The primary key is person_id and start_dt and I need to put a validation which avoids any overlapping addresses. Overlap as in there can be only 1 active address for a given start and end date range. Does HTMLDB has something like :new.start_dt the way we can write database triggers ? Please suggest a way to do this.
Lastly, how does HTMLDB handles error messages raised by table triggers. Can they be shown along with the item on the page as we can with the other HTMLDB validations ? I have many tables with all sorts of triggers and if any validation fails I generally do...raise_application_error(-20001,get_my_message(234));
get_my_message function returns the message text for message number 234 . Will this message be displayed somewhere or not ? Do I have to duplicate my validations , once in the triggers and then in HTMLDB as well ?