se você RDBMS suporta a função de janela,
para
SQL Server 2012
SELECT Qty,
SUM(Qty) OVER (ORDER BY Qty) AS CumulativeTOTAL
FROM tableName
para
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;