STATISTICS APPLICATION

Hello everyone,
I am building a web app in rails to manage quality indicators of a financial institution. My apps use many complexe Queries. Unfortunately I am not very strong in rails so for my query I use simple sql but my problems is that I don't know where is the best place to write my functions that must execute a specifics queries when it's call. I would like to be able to call my functions form my views so where I must write my function to get the job done?

Actually I wrote it in my controller but my countroller is becoming too long due to the number of functions so any advices are welcome

Best regards.