Oracle de pagination SQL

SELECT * FROM (
    SELECT a.*, rownum rn
    FROM (
        SELECT * FROM ORDERS WHERE CustomerID LIKE 'A%'
        ORDER BY OrderDate DESC, ShippingDate DESC
    ) a
    WHERE rownum < ((pageNumber * pageSize) + 1 )
)
WHERE rn >= (((pageNumber-1) * pageSize) + 1);
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