Derived_Tables_And_Correlated_Subqueries

SELECT DISTINCT PurchaseOrderNumber
FROM Sales.SalesOrderHeader h
INNER JOIN sales.SalesOrderDetail d
ON h.SalesOrderId = d.SalesOrderId
WHERE d.CarrierTrackingNumber = N'E257-40A1-A3'

SELECT PurchaseOrderNumber
FROM Sales.SalesOrderHeader h
INNER JOIN (SELECT DISTINCT d.SalesOrderId
            FROM Sales.SalesOrderDetail d
            WHERE d.CarrierTrackingNumber = N'E257-40A1-A3'
            ) d
ON h.SalesOrderId = d.SalesOrderId

SELECT PurchaseOrderNumber
FROM Sales.SalesOrderHeader h
WHERE EXISTS (SELECT *
            FROM Sales.SalesOrderDetail d
            WHERE d.CarrierTrackingNumber = N'E257-40A1-A3'
            AND h.SalesOrderId = d.SalesOrderId