Manual Tabular Form using checksum

Question

I have a manual tabular form which updates OK but when I add the htmldb_item.mds_checksum it does not always work. It does not pass the MD5 checksum test in the update process. Sometimes it works some times it does not. No one else is updating this data so it should pass the checksum error.
I need a manual tabular form so I can to retrieve this same data in a collection if the page is submitted for a cascading dropdown in another region. That is correct?
Of course, I could do the cascading dropdown another way instead of select list on submit. This is puzzling me.
Here is the sql query:
select htmldb_item.hidden(1,sub_id) sub_id,
htmldb_item.display_and_save(2,column_id) column_id,
htmldb_item.display_and_save(3,column_name) column_name,
htmldb_item.display_and_save(4,primary_key) primary_key,
htmldb_item.display_and_save(5,required) required,
htmldb_item.select_list(6,isselected,'Yes;Y,No;N') isselected,
htmldb_item.md5_checksum(isselected) cks
from sub_columns
where sub_id = :P26_SUB_ID
order by 2
Here is the update process:
declare
l_cks wwv_flow_global.vc_arr2;
j pls_integer := 1;
begin
-- Get original MD5 checksum
select wwv_flow_item.md5(isselected) cks
BULK COLLECT INTO
l_cks
from sub_columns
where sub_id = :P26_SUB_ID;
for i in 1..l_cks.count
loop
if htmldb_application.g_fcs(i) != l_cks(i) then
rollback;
raise_application_error(-20001,
'Current version of data in database has changed '||
'since user initiated update process.');
end if;
end loop;
-- update Subscription
for i in 1..htmldb_application.g_f01.count
loop
update sub_columns
set isselected = replace(htmldb_application.g_f06(i),'%'||'null%',NULL)
where sub_id = :P26_SUB_ID and
column_id = htmldb_application.g_f02(i);
end loop;
commit;
end;
Any help would be appreciated. I just don't see what I am doing wrong and I don't see any other way to do it.

Answer 1

I had already read this paper before doing the tabular form manually. I tried to follow it as closely as I could. My tabular form is a little different since I have a where clause in my SQL and only updating one field. The other fields are display_and_save. And I was branching to a different page than the page containing the tabular form. I would think none of these differences should make it not work. I did change to branch to the same page. That made no difference.
I did not need to do an insert so I skipped doing that step and then went to Adding Optimistic Locking. It is failuring in my update process with this code:
-- Get original MD5 checksum
select wwv_flow_item.md5(isselected) cks
BULK COLLECT INTO
l_cks
from sub_columns
where sub_id = :P26_SUB_ID;
for i in 1..l_cks.count
loop
if htmldb_application.g_fcs(i) != l_cks(i) then
rollback;
raise_application_error(-20001,
'Current version of data in database has changed '||
'since user initiated update process.');
end if;
end loop;
I get the Error process message and then the above -20001 error message when I click on the Submit button. Is there something wrong with my above code? I would assume I would need to add the where clause to the above select since I am only updating whose records.
I had created a submit button with action submit page and redirect to URL. The process executes on the condition when the submit button is pressed.
I need to get this working soon. I would assume other people have done a similar thing. I have tried many things. Another thing I notice is if I tell it to not display the first column, sub_id, and the last column, cks, (unselecting display in Report Attributes section) then the update does not work. I must be doing something wrong but I don't know what.
I created the page with component, report, SQL Report, and region type SQL Query.