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DECLARE @months int;
SELECT @months = DATEDIFF(MONTH, MAX(OrderDate), GETDATE())
FROM Sales.SalesOrderHeader;
UPDATE Sales.SalesOrderHeader SET DueDate = DATEADD(MONTH, @months-1, DueDate);
UPDATE Sales.SalesOrderHeader SET ShipDate = DATEADD(MONTH, @months-1, ShipDate);
UPDATE Sales.SalesOrderHeader SET OrderDate = DATEADD(MONTH, @months-1, OrderDate);
94395 rows affected