How to Create a Parameterized Report - The select "- ALL-" for department and manager not working.

Question

I downloaded the OEHR Sample Objects application and followed the steps in Oracle® Application Express Advanced Tutorials
Release 3.2.
The parameters and report seem to be working correctly except when I enter "all" for department or manager I get no matching hits.
What's the most efficient way to retrieve "all" if the users selects all for dept and mgr - thus we'd want to return all records in the table.
Region snipprt
Enter Search
Search Employee
Dept
- ALL -
Administration
Marketing
Purchasing
Human Resources
Shipping
IT
Public Relations
Sales
Executive
Finance
Accounting
Treasury
Corporate Tax
Control And Credit
Shareholder Services
Benefits
Manufacturing
Construction
Contracting
Operations
IT Support
NOC
IT Helpdesk
Government Sales
Retail Sales
Recruiting
Payroll
Mgr
- ALL -
Steven King
Neena Kochhar
Lex De Haan
Alexander Hunold
Nancy Greenberg
Den Raphaely
Matthew Weiss
Adam Fripp
Payam Kaufling
Shanta Vollman
Kevin Mourgos
John Russell
Karen Partners
Alberto Errazuriz
Gerald Cambrault
Eleni Zlotkey
Michael Hartstein
Shelley Higgins
The following is the sql that was provided as part of the turitoral.
SELECT
   "OEHR_EMPLOYEES"."EMPLOYEE_ID" "EMPLOYEE_ID",
   "OEHR_EMPLOYEES"."FIRST_NAME" "FIRST_NAME",
   "OEHR_EMPLOYEES"."LAST_NAME" "LAST_NAME",
   "OEHR_EMPLOYEES"."EMAIL" "EMAIL",
   "OEHR_EMPLOYEES"."PHONE_NUMBER" "PHONE_NUMBER",
   "OEHR_EMPLOYEES"."HIRE_DATE" "HIRE_DATE",
   "OEHR_EMPLOYEES"."JOB_ID" "JOB_ID",
   "OEHR_EMPLOYEES"."SALARY" "SALARY",
   "OEHR_EMPLOYEES"."COMMISSION_PCT" "COMMISSION_PCT",
   "OEHR_EMPLOYEES"."MANAGER_ID" "MANAGER_ID",
   "OEHR_EMPLOYEES"."DEPARTMENT_ID" "DEPARTMENT_ID"
FROM
   "#OWNER#"."OEHR_EMPLOYEES" "OEHR_EMPLOYEES"
WHERE
     (lower(first_name) like '%' || lower(:P1_NAME) || '%' OR
      lower(last_name) like '%' || lower(:P1_NAME) || '%')
AND department_id = decode(:P1_DEPT,'%null%',department_id,:P1_DEPT)
AND manager_id = decode(:P1_MGR,'%null%',manager_id,:P1_MGR)

Answer 1

Hi,
Use this..
SELECT
   "OEHR_EMPLOYEES"."EMPLOYEE_ID" "EMPLOYEE_ID",
   "OEHR_EMPLOYEES"."FIRST_NAME" "FIRST_NAME",
   "OEHR_EMPLOYEES"."LAST_NAME" "LAST_NAME",
   "OEHR_EMPLOYEES"."EMAIL" "EMAIL",
   "OEHR_EMPLOYEES"."PHONE_NUMBER" "PHONE_NUMBER",
   "OEHR_EMPLOYEES"."HIRE_DATE" "HIRE_DATE",
   "OEHR_EMPLOYEES"."JOB_ID" "JOB_ID",
   "OEHR_EMPLOYEES"."SALARY" "SALARY",
   "OEHR_EMPLOYEES"."COMMISSION_PCT" "COMMISSION_PCT",
   "OEHR_EMPLOYEES"."MANAGER_ID" "MANAGER_ID",
   "OEHR_EMPLOYEES"."DEPARTMENT_ID" "DEPARTMENT_ID"
FROM
   "#OWNER#"."OEHR_EMPLOYEES" "OEHR_EMPLOYEES"
WHERE
    (:P1_NAME IS NULL OR
        (:P1_NAME IS NOT NULL AND
                (lower(first_name) like '%' || lower(:P1_NAME) || '%') OR
                (lower(last_name) like '%' || lower(:P1_NAME) || '%')
    ) AND
    (:P1_DEPT IS NULL OR department_id = :P1_DEPT) AND
    (:P1_MGR IS NULL OR manager_id = :P1_MGR)