Select Highest volume clients based on certain criteria

Hi There,

I have a file of 5 million records in a csv file which I have created a table based on client ID and volume of transactions. What I now want to do is select the top 5 or 10 clients (based on client ID) with highest volume and returning all fields in the input file. 

ClientID   Volume

AB1              1,500,00

AB2               500,000

AB3               200,000

AB4               100,000

AB5                 50,000

What is the best way to do this, also 1 particular client has 1.5 million transactions which is more than 1 million rows in excel (I need the output in excel) and would need that split into 2 tabs.

Any suggestions on how to do this?

Thanks Jodi