Appian Database Read Only Access

At present at "Appian Administration Console", to create a user, there are only two user types are available, "Basic User" and "System Administrator".

Now to provide access to the Appian Database to a person, an user with "System Administrator" access permission is required to create. That case the person will get Read and Write both permissions to the Database. I want to create a user who will have only Read permission to the Appian Database. How can I do this?

I shall be grateful if anyone kindly help me regarding this.