SELECT * FROM 
(SELECT 
a.ArticleNumber
, a.ArticleDescription
, c.CountryName
, s.sales_quantity
, s.sales_amount
FROM Articles a
LEFT JOIN SalesSummary s on a.ArticleNumber = s.ArticleNumber
INNER JOIN Countries c on s.CountryCode = c.CountryCode) Data
PIVOT
(
  SUM(sales_quantity)
  FOR CountryName
  IN (
    [USA] ,[CANADA] , [MEXICO] ,[BRAZIL] ,[ARGENTINA]
     )
) PivotTable

SELECT 
a.ArticleNumber
, a.ArticleDescription
,SUM(CASE WHEN c.CountryName = 'USA' THEN sales_quantity ELSE 0 END) AS [USAQty]
,SUM(CASE WHEN c.CountryName = 'CANADA' THEN sales_quantity ELSE 0 END) AS [CANADAQty]
,SUM(CASE WHEN c.CountryName = 'MEXICO' THEN sales_quantity ELSE 0 END) AS [MEXICOQty]
,SUM(CASE WHEN c.CountryName = 'BRAZIL' THEN sales_quantity ELSE 0 END) AS [BRAZILQty]
,SUM(CASE WHEN c.CountryName = 'ARGENTINA' THEN sales_quantity ELSE 0 END) AS [ARGENTINAQty]
,SUM(CASE WHEN c.CountryName = 'USA' THEN sales_amount ELSE 0 END) AS [USAAmt]
,SUM(CASE WHEN c.CountryName = 'CANADA' THEN sales_amount ELSE 0 END) AS [CANADAAmt]
,SUM(CASE WHEN c.CountryName = 'MEXICO' THEN sales_amount ELSE 0 END) AS [MEXICOAmt]
,SUM(CASE WHEN c.CountryName = 'BRAZIL' THEN sales_amount ELSE 0 END) AS [BRAZILAmt]
,SUM(CASE WHEN c.CountryName = 'ARGENTINA' THEN sales_amount ELSE 0 END) AS [ARGENTINAAmt]
FROM Articles a
LEFT JOIN SalesSummary s on a.ArticleNumber = s.ArticleNumber
INNER JOIN Countries c on s.CountryCode = c.CountryCode
GROUP BY a.ArticleNumber
, a.ArticleDescription