Splitting table by column value - sql

Question

I have 4 tables I want to join to display items sold and items returned. The issue I'm having is that the sold and returned items are in the same table and I'm having trouble returning a 0 for the 'Return' column when an item is sold without returns and a 0 for the 'Sold' column when an item is returned without a sale. Here's what I'm trying to do,
Locations
LocationID LocationName
1 NY
2 LA
3 Chicago
Items
ItemID ItemName
A Sandwich
B Salad
C Wrap
Deliveries
DeliveryID LocationID
1 1
2 2
3 3
4 1
DeliveryRecords
RecordID DeliveryID ItemID Quantity RecordType
1 1 A 3 SOLD
2 1 B 4 SOLD
3 1 C 5 SOLD
4 1 C 2 RETURN
5 2 A 3 SOLD
6 2 B 2 SOLD
7 3 B 2 SOLD
8 3 C 3 SOLD
9 4 A 1 RETURN
And I want my query to return,
Location DeliveryID Item Sold Returned
NY 1 Sandwich 3 0
NY 1 Salad 4 0
NY 1 Wrap 5 2
LA 2 Sandwich 3 0
LA 2 Salad 2 0
Chicago 3 Salad 2 0
Chicago 3 Wrap 3 0
NY 4 Wrap 0 1

Answer 1

I think you just want conditional aggregation (after a bunch of joins):
select l.locationname, dr.deliveryid, i.itemname,
sum(case when dr.recordtype = 'SOLD' then quantity else 0 end) as sold,
sum(case when dr.recordtype = 'RETURN' then quantity else 0 end) as returned
from deliveryrecords dr join
deliveries d
on dr.deliveryid = d.deliveryid join
location l
on d.locationid = l.locationid join
items i
on dr.itemid = i.itemid
group by l.locationname, dr.deliveridy, i.itemname;

Answer 2

Using JOIN and SUM:
SQL Fiddle
SELECT
l.LocationName,
dr.DeliveryID,
i.ItemName,
[Sold] = SUM(CASE WHEN dr.RecordType = 'SOLD' THEN dr.Quantity ELSE 0 END),
[Returned] = SUM(CASE WHEN dr.RecordType = 'RETURN' THEN dr.Quantity ELSE 0 END)
FROM DeliveryRecords dr
INNER JOIN Items i
ON i.ItemID = dr.ItemId
INNER JOIN Deliveries d
ON d.DeliveryID = dr.DeliveryID
INNER JOIN Locatins l
ON l.LocationID = d.LocationId
GROUP BY
dr.DeliveryID, l.LocationName, i.ItemName