Oracle - Converting a column to rows and getting a sum - sql

Question

Im trying to convert a column to rows and get a sum of the items ordered. Below is how the data is currently in the database. Notice how the DollarDays store gives the indication that not all stores have ordered all items.
Store ItemNumber Description Ordered
---- ---------- ---------- ---------
WallyMart 10021 Corn 10
J-Mart 10021 Corn 4
Big-H Foods 10021 Corn 32
WallyMart 20055 Beans 11
J-Mart 20055 Beans 3
Big-H Foods 20055 Beans 21
DollarDays 50277 Onions 48
This is my goal below. It looks to be pretty much grouping by ItemNumber
ItemNumber Description WallyMart J-Mart Big-H Foods DollarDays TotalOrdered
---------- ----------- --------- ------ ----------- ---------- ------------
10021 Corn 10 4 32 0 46
20055 Beans 11 3 21 0 35
50277 Onions 0 0 0 48 48
When I try PIVOT this is shortened example of what I get. Im totally lost.
ItemNumber Description WallyMart J-Mart Big-H Foods DollarDays
---------- ----------- --------- ------ ----------- ----------
10021 Corn 10 Null Null Null
10021 Corn Null 4 Null Null
10021 Corn Null Null 32 Null
10021 Corn Null Null Null 0
FYI I am of course a beginner and a student so please forgive me I haven't posted exactly right.
Any help is appreciated.

Answer 1

Try this:
select
itemnumber, description,
coalesce("WallyMart",0) as "WallyMart",
coalesce("J-Mart",0) as "J-Mart",
coalesce("Big-H Foods",0) as "Big-H Foods",
coalesce("DollarDays",0) as "DollarDays",
coalesce("WallyMart",0) + coalesce("J-Mart",0) + coalesce("Big-H Foods",0) + coalesce("DollarDays",0) as "Total"
from
(select * from stores) s
pivot
(max(ordered)
for store in
('WallyMart' as "WallyMart",
'J-Mart' as "J-Mart",
'Big-H Foods' as "Big-H Foods",
'DollarDays' as "DollarDays")) p
To explain a bit, the PIVOT clause consists of 2 parts - the aggregation and the list of values used for this aggregation. For your case, the aggregation used is MAX, since it looks like one store can have only one record for a particular product. If that is not so, SUM would be the right function to use. Likewise, since we want store-wise details, and not product-wise, we specify the distinct values of the store column in the list.
COALESCE is used to default null values in the ordered column to 0. Finally, we add the 4 derived columns (after coalescing to 0) to get the total value.
SQLFiddle