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Account Jan Feb Mar Apr etc…
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SELECT   [NewSalesHistory].[Region]
                ,[NewSalesHistory].[ShipTo]
               ,SUM(case when [NewSalesHistory].[billingdate] between '6/1/2016' and '6/30/2016' then newbillingdata else 0 end ) + [X].[Jun-16]  AS 'Jun-16'
FROM [NewSalesHistory]
FULL join    (SELECT      [Shipto]
                 ,SUM(case when [BWLease].[billingdate] between '6/1/2016' and '6/30/2016' then ExtPrice else 0 end ) as 'Jun-16'
FROM [AirgasPricing].[dbo].[BWLease]
  GROUP BY [Shipto]) X ON [NewSalesHistory].[ShipTo] = [X].[Shipto]

GROUP BY [NewSalesHistory].[Region]
            ,[NewSalesHistory].[ShipTo]
,[X].[Jun-16]