Banking Recipe

[Andy]

Im well versed in Java/Hibernate/RDBMS.  Im trying to get my head around how 
NoSQL does not use transactions.
I read the Banking Recipe which didn't really do the job: 
http://guide.couchdb.org/draft/recipes.html
So if I wanted to write an online banking app, I would have say a million 
Transaction Documents, and to find a persons balance I would need to sum all 
transactions?  There must be a better way.