Sorry, but you've confused me.  First you said the source is SQL, now you're saying it's .txt.  But if it's .txt, just bring it into a staging table - as you already appear to have done - and manipulate it from there.  If you're not very good in SQL then that's going to be a problem for you.  I'm happy to help out, but I need you to tell me where you're stuck.

John