se il tuo RDBMS supporta la funzione finestra,
per SQL Server 2012
SELECT Qty,
SUM(Qty) OVER (ORDER BY Qty) AS CumulativeTOTAL
FROM tableName
per SQL Server 2008
SELECT a.Qty, (SELECT SUM(b.Qty)
FROM TableName b
WHERE b.Qty <= a.Qty)
FROM TableName a
ORDER BY a.Qty;