Show 0 Not Null With Pivot - sql-server-2008

Question

Why is my Coalesce() statement in my initial Select statement not replacing the Null with a 0?
Select * From
(
Select a.orderstatus As [Stat], Coalesce(Count(b.id), '0') As [Count], b.region
From orderstatus a
Left Join saleinfo b
on b.orderstatus = a.orderstatus
Group By a.orderstatus, b.region
) one
pivot ( Max([Count]) For region In ([East], [West], [North], [South]) ) pv

Answer 1

Because you are using it in the inner query, whereas the problem is that the record doesn't it exist so the PIVOT is creating the NULL after the inner query has been processed. If your query (one) returned:
Stat Count Region
-------------------------
Stat1 0 East
Stat2 2 East
Stat1 5 West
You will end up with a Pivot Table like
Stat East West North South
---------------------------------------
Stat1 0 5 NULL NULL
Stat2 2 NULL NULL NULL
For example you get NULL for (Stat2, West) because there is no result in your subquery, so the COALESCE does not help. Your work around would be to just use COUNT in the PIVOT itself:
SELECT pvt.OrderStatus, pvt.East, pvt.West, pvt.North, pvt.South
FROM ( SELECT os.OrderStatus, si.Region, si.ID
FROM OrderStatus AS os
LEFT JOIN SaleInfo AS si
ON si.OrderStatus = b.OrderStatus
) AS t
PIVOT
( COUNT(ID)
FOR Region IN ([East], [West], [North], [South])
) AS pvt;
Or to put the COALESCE in the outer select:
SELECT pvt.OrderStatus,
East = COALESCE(pvt.East, 0),
West = COALESCE(pvt.West, 0),
North = COALESCE(pvt.North, 0),
South = COALESCE(pvt.South, 0)
FROM ( SELECT os.OrderStatus, si.Region, [Count] = COUNT(si.ID)
FROM OrderStatus AS os
LEFT JOIN SaleInfo AS si
ON si.OrderStatus = b.OrderStatus
) AS t
PIVOT
( MAX([Count])
FOR Region IN ([East], [West], [North], [South])
) AS pvt;
I much prefer the first option though.
EDIT
Example showing 0 returned for non existent data when using COUNT:
SELECT pvt.Stat, pvt.East, pvt.West, pvt.North, pvt.South
FROM (VALUES
('Stat1', 'East', 1),
('Stat2', 'East', 2),
('Stat1', 'West', 3)
) t (Stat, Region, ID)
PIVOT
( COUNT(ID)
FOR Region IN ([East], [West], [North], [South])
) AS pvt;