Will a Union handle this? Showing aggregates from different groups on the same row

Question

So I want to display a result that includes a sum of the transaction amount for a list of orders.  Each order can have items, and each item has a transaction amount.  
Then I have a goal table that keeps track of the "goals" set for a simple forecasting method used by sales.  A goal is defined for each item type and a count.
Table structures are like this
DECLARE @OrderTran AS TABLE(RowId INT PRIMARY KEY IDENTITY(1,1) NOT NULL, OrderId INT, ItemId INT, ItemAmount DECIMAL(10,2) )
DECLARE @GoalData AS TABLE(RowId INT PRIMARY KEY IDENTITY(1,1) NOT NULL, ItemTypeKey INT, ItemGoalCount INT )
The problem with getting totals for both order transactions AND goals, is there there might not be items in some of the orders for the items that goals set for.  So If I grab the order totals first, then left join on goals, I still might miss out some
of the goal results when I do an aggregate.
Should union help here?
In other words, get a result from the order totals
Then get a similar result from the goals
Then union the 2 results?

Answer 1

Are you looking for something like below:
DECLARE @OrderTran AS TABLE(RowId INT PRIMARY KEY IDENTITY(1,1) NOT NULL, OrderId INT, ItemId INT, ItemAmount DECIMAL(10,2) )
DECLARE @GoalData AS TABLE(RowId INT PRIMARY KEY IDENTITY(1,1) NOT NULL, ItemTypeKey INT, ItemGoalCount INT )
INSERT INTO @OrderTran
VALUES (1, 1, 10), (2, 1, 22), (3, 2, 12), (4, 1, 50), (5, 2, 100)
INSERT INTO @GoalData
VALUES (1, 100), (3, 200)
SELECT
COALESCE(O.ItemID, G.ItemTypeKey, 0) As ItemID
,O.TotalAmount
,G.TotalGoalAmount
FROM
SELECT ItemId, SUM(ItemAmount) As TotalAmount
FROM
@OrderTran
GROUP BY
ItemID
) O
FULL OUTER JOIN
SELECT ItemTypeKey, SUM(ItemGoalCount) As TotalGoalAmount
FROM
@GoalData
GROUP BY
ItemTypeKey
) G ON O.ItemID = G.ItemTypeKey
Output
ItemID | TotalAmount
| TotalGoalAmount
1 | 82.00
| 100
2 | 112.00
| NULL
3 | NULL
| 200
Best Wishes, Arbi; Please vote if you find this posting was helpful or Mark it as answered.