Master Detail Forms with 2 composite primary keys - Is there a workaround?

Question

Hello All,
I have been searching for a workaround to the maximum 2 part primary key restriction on the multi-row updates, and master-detail forms, and am hoping that someone can help me. I am using HTMLDB v2.0.0.00.49 with IE 6 against a 9.2 DB.
I successfully implemented the workaround of Fred Stoopendaal's (see Updata PK on HTML DB ) and it works fine for single page multi-record updateable forms, but alas I haven't been able to extend it to master detail forms (I think it is something to do with Oracle not allowing the "returning" clause on views).
Here is what I tried:
two tables, one with a 2 part composite primary key, which is the master table, and a detail table with 3 part composite primary key -
--------- BEGIN SQL ---------
create table master_table
( master_col1 number
, master_col2 number
, master_col3 varchar2(30)
, constraint master_pk primary key (master_col1,master_col2));
create table detail_table
(detail_col1 number
,detail_col2 number
,detail_col3 number
,detail_col4 varchar2(30)
, constraint detail_pk primary key(detail_col1,detail_col2,detail_col3)
, constraint master_detail_fk foreign key (detail_col1,detail_col2) references master_table(master_col1,master_col2));
create or replace view v_master_table as
select rowid mata_rowid,mata.*
from master_table mata;
create or replace view v_detail_table as
select rowid deta_rowid,
(select rowid from master_table mata where mata.master_col1 = deta.detail_col1 and mata.master_col2 = deta.detail_col2) deta_mata_rowid
, deta.*
from detail_table deta;
create or replace trigger mata_ins_upd_trg
instead of insert or update on v_master_table
referencing new as new old as old
for each row
begin
if inserting then
insert into master_table (master_col1, master_col2, master_col3)
values (:new.master_col1, :new.master_col2, :new.master_col3);
end if;
if updating then
update master_table
set master_col1 = :new.master_col1,
master_col2 = :new.master_col2,
master_col3 = :new.master_col3
where rowid = :old.mata_rowid;
end if;
end;
create or replace trigger deta_ins_upd_trg
instead of insert or update on v_detail_table
referencing new as new old as old
for each row
begin
if inserting then
insert into detail_table ( detail_col1, detail_col2, detail_col3, detail_col4)
values (:new.detail_col1, :new.detail_col2, :new.detail_col3, :new.detail_col4);
end if;
if updating then
update detail_table
set detail_col1 = :new.detail_col1,
detail_col2 = :new.detail_col2,
detail_col3 = :new.detail_col3,
detail_col4 = :new.detail_col4
where rowid = :old.deta_rowid;
end if;
end;
--------- END SQL ---------
Then I created a master-detail form in Apex on the two views, using the mata_rowid and deta_rowid as primary keys, and mata_rowid=deta_mata_rowid as the link. I realise that using a function to fetch the master rowid within the detail view query is costly, but it was my intention to modify the record fetch queries to use the real FK columns once things were up and running.
It seems to generate the pages ok, and I can insert/update master table records, but as soon as I modify records in the detail table things go a bit haywire. I can't find any documentation on how the inbuilt MRU/MRD logic works, so can't figure out the issue.
Can anyone out there tell me what the problem is with the logic above, or if they have come up with a neat solution to this annoying limitation. I know that many will say that I should modify the data model to use surrogate primary keys, but many of the uses for HTMLDB are new interfaces for old schemas, so a workaround that doesn't involve wholesale data model changes would be preferable.
Thanks in advance,
Mike Cretan

Answer 1

Hi, this is likely not the most elegant way...but perhaps the simplest -- and I didn't have much time to play.
I used Wizard to create two separate Master Detail forms, each with a separate detail table. Thus I ended up with four pages:
Page "A" - "Selector" page for Master (Report), with Edit link driving to Detail-1
Page "B" - Editable Master/Detail-1 page (HTML / Report)
Page "C" - "Selector" page for Master (Report), with Edit link driving to Detail-2
Page "D" - Editable Master/Detail-2 page (HTML / Report)
Then I selected the primary key column TWICE on the Report on Page A. Modified the second instance of this column to navigate to Page D (passing primary key) exactly the way the original instance of this column navigates to Page B. Then I deleted Page C.
Since you can have only one Tabular Entry form per page, this seemed the best way to drive two separate detail tables from a common interface.