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Oracle Tips by Burleson |
Parent
Child Select Lists
There have been several questions on how to do
this on the HTML DB forum, so I figure I’d better cover the topic. A
Parent/Child select list is two select lists working together. The
child select list is populated based on the selection from the parent
select list. So, if there are stores and departments, it would be
desirable to select a store and then have the child select list
populate with all the departments in that store. Furthermore, it
would not be desirable to have the departments select list populated
if there were no selection in the store select list.
Figure 10.23 shows a region having two select
lists. The following exercise shows how to create these two select
lists. To follow along, create a page in the Easy HTML DB Book
application with the page ID equal to 2908. To create the tables and
data use the file name parent_child_tables.sql in the online code
depot.
Creating the Store
Select List
1.
Click on the create item button in the Items area of the Page
Rendering region.
2.
Choose the Select List option and click Next.
3.
Choose the Select List with Redirect option and click Next.
Use of this option is not desirable in all
cases. The reason is if the values in page items have not been saved
in session state, the values will be lost performing a submit when the
page is rendered again from the redirect. When page item values are
to be saved in session state, the Select List with Submit option
should be chosen.
4.
On the Display Position and Name page:
5.
On the List of Values page:
select name d, store_id r
from store
order by 1
This case uses a query, as opposed to an
LOV, to keep it simple. In reality it is better to use an LOV.
6.
On the Item Attributes page, fill in the desired information
and click Next. There is nothing special here pertaining to the
parent / child relationship.
7.
On the source page, enter -1 as the text for the Default value
and click the Create Item button. A numeric value is used here since
the STORE_ID column is numeric.
Creating the Department
Select List
1.
Click on the create item button in the Items area of the Page
Rendering region.
2.
Choose the Select List option and click Next.
3.
Choose the Select List option again and click Next.
This time there is no special action
needed from the Select List when an item is selected.
4.
Enter the Item Name, Sequence, and Region information and click
Next.
5.
On the List of Values page:
-
Named LOV: leave this alone
-
Display Null Option: YES.
-
Null Text: - Select a Department -
-
Null Value: -1 because the column
return value is numeric.
-
List of Values Query: Enter the text
shown in Figure 10.24
-
Click Next.
This time something special must be done
for the List of Values page. It is not desirable to create an LOV
with a WHERE clause for this, so the select statement for the LOV will
be provided right in the item definition as shown in Figure 10.18.
The query uses the page item name from the parent select list,
P2908_STORE_ID, to only select the departments associated with the
store selected.
6.
Again, the Item Attributes are not important for the outcome of
the parent / child select list. Leave the default values and click
Next.
7.
On the Source page, enter X for the Default value and click the
Create Item button.
8.
Run the report and see the Parent / Child select lists in
action.
The above book excerpt is from:
Easy HTML-DB
Oracle Application Express
Create
Dynamic Web Pages with OAE
ISBN 0-9761573-1-4
Michael Cunningham & Kent Crotty
http://www.rampant-books.com/book_2005_2_html_db.htm
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