Ruby on Rails

Ruby,

I have a collection of Postgres tables I want my users to be able to access (share)but not modify on my Rails website .  I want each of them to be able to extract data from the tables using whatever SQL they wish and for each user not to be able to interact with other users' extracted data.

I have Devise working to give access to each separate user but now I need/want suggestions as to how to link a Devise authorized user with a correspondingly named Postgres user.

Suggestions would be appreciated.

Ralph Shnelvar