Question

currently the stored proc returns one record based on a employee_number that is passed as a parameter. If the surpervisor_id is NULL, there is no record returned. If I want to return a record with all the other fields, and have a NULL in the supervisor_id field, how would I configure that?

SELECT DISTINCT 
    tblPeople.PERSON_ID, tblPeople.FIRST_NAME, tblPeople.LAST_NAME, 
    tblPeople.EMPLOYEE_NUMBER, tblPeople.EMAIL_ADDRESS, 
    tblAddress.ADDRESS_LINE1, tblAddress.ADDRESS_LINE2, tblAddress.ADDRESS_LINE3, 
    tblAddress.TOWN_OR_CITY, tblAddress.STATE, tblAddress.COUNTRY, 
    tblAddress.POSTAL_CODE, tblPeople.PHONE_NUMBER, 
    tblPeople.EFFECTIVE_START_DATE, tblPeople.EFFECTIVE_END_DATE, 
    tblLocation.LOC_CODE, 
    pp2.FIRST_NAME AS Expr1, pp2.LAST_NAME AS Expr2, 
    pp2.EMPLOYEE_NUMBER AS Expr3, tblAssignment.SUPERVISOR_ID, 
    tblAssignment.ATTRIBUTE2, tblAssignment.ATTRIBUTE3, 
    tblPeople.INSTANCE_ID, tblAssignment.LOC_ID
FROM
    tblPeople AS tblPeople 
RIGHT OUTER JOIN
    tblAddress AS tblAddress ON tblPeople.PERSON_ID = tblAddress.PERSON_ID 
                             AND tblPeople.INSTANCE_ID = tblAddress.INSTANCE_ID 
INNER JOIN
    tblAssignments AS tblAssignment ON tblPeople.PERSON_ID = tblAssignment.PERSON_ID 
                                    AND tblPeople.INSTANCE_ID = tblAssignment.INSTANCE_ID 
INNER JOIN
    Locations AS Location ON Location.LOC_ID = tblAssignment.LOC_ID
                          AND Location.INSTANCE_ID = tblAssignment.INSTANCE_ID 
INNER JOIN 
    tblPeople AS pp2 ON pp2.PERSON_ID = tblAssignment.SUPERVISOR_ID
                     AND pp2.INSTANCE_ID = tblAssignment.INSTANCE_ID
WHERE     
    tblPeople.EMPLOYEE_NUMBER = '3298'
    AND tblPeople.INSTANCE_ID = 1
    AND tblAssignment.Assignment_Status = 'Current'

Answer 1

Most likely, you just need to change this JOIN

INNER JOIN 
    tblPeople AS pp2 ON pp2.PERSON_ID = tblAssignment.SUPERVISOR_ID
                     AND pp2.INSTANCE_ID = tblAssignment.INSTANCE_ID

to an LEFT OUTER JOIN

LEFT OUTER JOIN 
    tblPeople AS pp2 ON pp2.PERSON_ID = tblAssignment.SUPERVISOR_ID
                     AND pp2.INSTANCE_ID = tblAssignment.INSTANCE_ID

If that SUPERVISOR_ID IS NULL, then the columns from the pp2 table will be NULL, but you should still get data for all other columns back.