SQL & PL/SQL

If someone could help me figure out what joins I need to do to handle the following, I would be greatly appreciative.

Our Oracle Order Order Header has flex fields that are used to track a special address by it's code which is stored in Attribute 13 on OE_ORDER_HEADERS_ALL table. We use a site usage code called ADMIN_BY to set up a site in the customers table so we can place the address we are linking here. So for instance, if the order had AB-XXXXXX in it's attribute 13 field, I want to look for this same code in the customer site usage table and find the address in HZ_LOCATIONS table or null if attribute 13 does not have data. My only problem is taking care of the NULL case for all previous orders that did not contain this information.

This is my sql query whcih works if we have a valid entry in attribute 13. This is also set up for a specific order number for testing only.

SELECT DISTINCT
ONT.OE_ORDER_HEADERS_ALL.ORDER_NUMBER, AR.HZ_LOCATIONS.LOCATION_ID, AR.HZ_PARTY_SITES.LOCATION_ID AS LOC_ID,
AR.HZ_PARTY_SITES.PARTY_SITE_ID, AR.HZ_PARTY_SITES.PARTY_ID, ONT.OE_ORDER_HEADERS_ALL.SOLD_TO_ORG_ID,
ONT.OE_ORDER_HEADERS_ALL.ATTRIBUTE13, ONT.OE_ORDER_HEADERS_ALL.ATTRIBUTE14, AR.HZ_LOCATIONS.ADDRESS1,
AR.HZ_CUST_ACCT_SITES_ALL.PARTY_SITE_ID AS P_SITE_ID, AR.HZ_CUST_ACCT_SITES_ALL.CUST_ACCT_SITE_ID,
AR.HZ_CUST_SITE_USES_ALL.CUST_ACCT_SITE_ID AS CUST_ACCT_S_ID, AR.HZ_CUST_SITE_USES_ALL.SITE_USE_CODE
FROM AR.HZ_PARTY_SITES, AR.HZ_LOCATIONS, ONT.OE_ORDER_HEADERS_ALL, AR.HZ_CUST_ACCT_SITES_ALL, AR.HZ_CUST_SITE_USES_ALL
WHERE AR.HZ_PARTY_SITES.LOCATION_ID = AR.HZ_LOCATIONS.LOCATION_ID AND
AR.HZ_PARTY_SITES.PARTY_ID = ONT.OE_ORDER_HEADERS_ALL.SOLD_TO_ORG_ID AND
AR.HZ_PARTY_SITES.PARTY_SITE_ID = AR.HZ_CUST_ACCT_SITES_ALL.PARTY_SITE_ID AND
AR.HZ_CUST_ACCT_SITES_ALL.CUST_ACCT_SITE_ID = AR.HZ_CUST_SITE_USES_ALL.CUST_ACCT_SITE_ID AND
ONT.OE_ORDER_HEADERS_ALL.ATTRIBUTE13 = AR.HZ_CUST_SITE_USES_ALL.LOCATION AND
(ONT.OE_ORDER_HEADERS_ALL.ORDER_NUMBER = TO_NUMBER('5074920')) AND (AR.HZ_CUST_SITE_USES_ALL.SITE_USE_CODE = 'ADMIN_BY')



I tried this code to no avail.

SELECT DISTINCT
ONT.OE_ORDER_HEADERS_ALL.ORDER_NUMBER, AR.HZ_LOCATIONS.LOCATION_ID, AR.HZ_PARTY_SITES.LOCATION_ID AS LOC_ID,
AR.HZ_PARTY_SITES.PARTY_SITE_ID, AR.HZ_PARTY_SITES.PARTY_ID, ONT.OE_ORDER_HEADERS_ALL.SOLD_TO_ORG_ID,
ONT.OE_ORDER_HEADERS_ALL.ATTRIBUTE13, ONT.OE_ORDER_HEADERS_ALL.ATTRIBUTE14, AR.HZ_LOCATIONS.ADDRESS1,
AR.HZ_CUST_ACCT_SITES_ALL.PARTY_SITE_ID AS P_SITE_ID, AR.HZ_CUST_ACCT_SITES_ALL.CUST_ACCT_SITE_ID,
AR.HZ_CUST_SITE_USES_ALL.CUST_ACCT_SITE_ID AS CUST_ACCT_S_ID, AR.HZ_CUST_SITE_USES_ALL.SITE_USE_CODE
FROM AR.HZ_PARTY_SITES, AR.HZ_LOCATIONS, AR.HZ_CUST_ACCT_SITES_ALL, ONT.OE_ORDER_HEADERS_ALL, AR.HZ_CUST_SITE_USES_ALL,
ONT.OE_ORDER_HEADERS_ALL OE_ORDER_HEADERS_ALL_1
WHERE AR.HZ_PARTY_SITES.LOCATION_ID = AR.HZ_LOCATIONS.LOCATION_ID AND
AR.HZ_PARTY_SITES.PARTY_SITE_ID = AR.HZ_CUST_ACCT_SITES_ALL.PARTY_SITE_ID AND
AR.HZ_PARTY_SITES.PARTY_ID = ONT.OE_ORDER_HEADERS_ALL.SOLD_TO_ORG_ID AND
AR.HZ_CUST_ACCT_SITES_ALL.CUST_ACCT_SITE_ID = AR.HZ_CUST_SITE_USES_ALL.CUST_ACCT_SITE_ID AND
AR.HZ_CUST_SITE_USES_ALL.LOCATION (+) = OE_ORDER_HEADERS_ALL_1.ATTRIBUTE13 AND
(ONT.OE_ORDER_HEADERS_ALL.ORDER_NUMBER = TO_NUMBER('5074920')) AND
(AR.HZ_CUST_SITE_USES_ALL.SITE_USE_CODE (+) = 'ADMIN_BY')

Any assistance would be greatly appreciated.