Save SQL Query Results in Variable
Solution 1:
You can use CTE to avoid looping, maybe like this:
with cte as (
SELECT ProductName, SUM(Quantity) AS ProductQuantity FROM
(SELECT CustomerID FROM Customers AS C
WHERE Country = 'Germany') AS CG
INNER JOIN Orders AS O
ON CG.CustomerID = O.CustomerID
INNER JOIN OrderDetails AS OD
ON O.OrderID = OD.OrderID
INNER JOIN Products as P
ON OD.ProductID = P.ProductID
GROUP BY ProductName
)
SELECT ProductName
FROM cte
where ProductQuantity = (SELECT MAX(ProductQuantity) FROM cte)