Using COALESCE with JOIN on a different database column - sql

Question

Trying to populate the location column of a query and was hoping that the use of the COALESCE function would help me get what I want.
SELECT OrderItem.Code AS ItemCode, MAX(COALESCE(OrderItem.Location, [Picklist].[dbo].[ItemData].InventoryLocation)) AS Location, SUM(OrderItem.Quantity) AS Quantity, MAX(Store.StoreName) AS Store
FROM OrderItem
INNER JOIN [Order] ON OrderItem.OrderID = [Order].OrderID
INNER JOIN [Store] ON [Order].StoreID = [Store].StoreID
LEFT JOIN [AmazonOrder] ON [AmazonOrder].OrderID = [Order].OrderID
JOIN [Picklist].[dbo].[ItemData] ON [Picklist].[dbo].[ItemData].[InventoryNumber] = [OrderItem].[Code]
WHERE (CASE WHEN [Order].[LocalStatus] = 'Recently Downloaded' AND [AmazonOrder].FulfillmentChannel = 2 THEN 1
WHEN [Order].[LocalStatus] = 'Recently Downloaded' AND [Store].StoreName != 'Amazon' THEN 1 ELSE 0 END ) = 1
GROUP BY OrderItem.Code
ORDER BY ItemCode
There will not be a location when the Store is Amazon so I need to Join on another table in another database. I don't believe I'm using this correctly. Also I do get the right Location results returned if I use :
SELECT InventoryLocation From [Picklist].[dbo].[ItemData] WHERE InventoryNumber = 'L1201-2W-EA'

Answer 1

Perhaps this is more like the query that you want:
SELECT oi.Code AS ItemCode, COALESCE(oi.Location, id.InventoryLocation) AS Location,
oi.Quantity, s.StoreName AS Store
FROM OrderItem oi INNER JOIN
[Order] o
ON oi.OrderID = o.OrderID INNER JOIN
[Store]
ON o.StoreID = s.StoreID LEFT JOIN
AmazonOrder ao
ON ao.OrderID = o.OrderID JOIN
[Picklist].[dbo].[ItemData] id
ON id.InventoryNumber = oi.[Code]
WHERE o.LocalStatus = 'Recently Downloaded' AND
(ao.FulfillmentChannel = 2 OR s.StoreName <> 'Amazon')
ORDER BY ItemCode
Here are the changes:
Removed the aggregation. It does not seem to be part of the question.
Introduced table aliases, so the query is easier to write and to read.
Simplified the logic in the where clause.

Answer 2

As the comment above says, the max seems somewhat strange, an arbitrary aggregation no doubt due to one of the joins bringing back more information than you might of expected.
Then the statement has a few issues:
The coalesce is using two fields, neither if which is in a left join, only the AmazonOrder is left joined, so that seems a bit strange, that would only work if the first field in the coalesce (OrderItem.Location) is nullable - which it might be, there is no schema posted.
The left join itself is an inner join in disguise at present - within the where clause you have given explicit conditions on a field from that table - AND [AmazonOrder].FulfillmentChannel = 2 - if the record was actually missing the left join would return null for that field, and the where clause would then drop it out of the results. If you want this to properly work as a left join, any condition on fields from that table must move into the join condition, or the where clause itself must allow for that field being null (explicitly or using a coalesce.)

Answer 3

SELECT OrderItem.Code AS Code,
CASE WHEN (LEN(ISNULL(MAX([OrderItem].[Location]),'')) = 1)
THEN MAX([OrderItem].[Location])
ELSE MAX([Picklist].[dbo].[ItemData].InventoryLocation)
END AS Location,
SUM(OrderItem.Quantity) AS Quantity,
MAX(Store.StoreName) AS Store
FROM OrderItem
INNER JOIN [Order] ON OrderItem.OrderID = [Order].OrderID
INNER JOIN [Store] ON [Order].StoreID = [Store].StoreID
LEFT JOIN [AmazonOrder] ON [AmazonOrder].OrderID = [Order].OrderID
LEFT JOIN [Picklist].[dbo].[ItemData] ON [Picklist].[dbo].[ItemData].[InventoryNumber] = [OrderItem].[Code] OR
[Picklist].[dbo].[ItemData].[MediaCreator] = [OrderItem].[Code]
WHERE [Order].LocalStatus = 'Recently Downloaded' AND (AmazonOrder.FulfillmentChannel = 2 OR Store.StoreName <> 'Amazon')
GROUP BY OrderItem.Code
ORDER BY OrderItem.Code
Decided to go with case statement on location column route because I could not get COALESCE to work for me. Schema, some not all data, at SQLFiddle.
I guess if someone gets COALESCE to work I'll change the answer?
#Gordon Linoff I used the re-written WHERE clause because it looked cleaner than using the CASE statement. It worked and guessed there was a simpler way to go about it but was more worried about getting COALESCE to work. As for the Aliases sometimes I like to use them but in this case since there was a lot of tables I like to code out what I'm actually working in. Just my preference .