How to make right outer join? - sql

Question

I am using OE schema and trying to see item # and quantity on hand in each warehouse and if any warehouse does not have item than it should show 0 item in hand. i am running following SQL and it is not showing 0 quantity for items.
select i.product_id,w.warehouse_name ,(i.quantity_on_hand)
from inventories i
right outer join warehouses w
on (i.warehouse_id=w.warehouse_id)
order by 1
I want to see result like this:
PRODUCT_ID WAREHOUSE_NAME NVL(I.QUANTITY_ON_HAND,0)
---------- ----------------------------------- -------------------------
2262 Sydney 35
2262 Beijing 50
2262 Bombay 35
2262 San Francisco 155
2262 Seattle, Washington 77
Toronto 0
New Jersey 0
Southlake, Texas 0
Mexico City 0
3501 Toronto 220
3501 Sydney 320
3501 Mexico City 294
3501 Beijing 268
3501 San Francisco 353
New Jersey 0
Southlake, Texas 0
Seattle, Washington 0
Bombay 0

Answer 1

You want to see a row for every warehouse and every product. So, start with generating this list and use left outer join to bring in the values that exist:
select i.product_id, w.warehouse_name, coalesce(i.quantity_on_hand, 0)
from warehouses w cross join
(select distinct product_id from inventories) p left join
inventories i
on w.warehouse_id = i.warehouse_id and p.product_id = i.product_id
order by i.product_id, w.warehouse_name;