Not In Query on select List

Question

Apex 4.2
Two Tables
SITES
  Site_id (pk)
  Site_name
  Date
ACTIVATION
   Activation_id (pk)
   Activation_date
   Deactivation_date
   Site_id (fk)
* I have a report based on the ACTIVATION table. Upon clicking an edit link on any row of the report, it takes you to a form to edit the information. The form allows you to edit the Site_id. The Site_id is represented as a select list with the following LOV query:
SELECT SITE_NAME, SITE_ID
FROM SITES
* This select list gives me all of the site_names, however, I want to filter this select list by only showing those sites that are not in the report. All of the site names are as follows:
Maryland
Los Angeles
Natchez
Bakersfield
Austin
The report has rows:
Activation ID     Site Name              Activation Date     Deactivation Date
  1                         Natchez                    3/11/2013         
  2                         Los Angeles               5/27/2020
I would like for the list to only display the ones that are not in the report, i.e. Austin, Bakersfield, Maryland.
I have tried to write a NOT IN query. When I click an edit link from the report to navigate to the form, the select list shows the list of entries that I desire, however, the row that I clicked shows the id of the Site Name instead of the actual name. I'm not sure where my error is. I hope all this makes sense. Thanks for your help in advance. Oh, and my query that I wrote is as follows:
SELECT SITE_NAME, SITE_ID
FROM SITES
WHERE SITE_ID NOT IN (SELECT SITE_ID
FROM ACTIVATION
WHERE this = that)

Answer 1

Hi,
This is because the query is excluding the current site you are trying to modify since it is actually in the report.
You can include in your query:
or site_id = :Pxx_SITE_ID
Where Pxx_SITE_ID is the item holding the site_id value and xx is your page number.
Thank you,
Erick