The difference between ROLE and PRIVILEGE for Oracle

Rick Byham has a WIKI post showing the fixed server and fixed database roles and how they map. You can look here: http://social.technet.microsoft.com/wiki/contents/articles/database-engine-fixed-server-and-fixed-database-roles.aspx

The chart shows that db_datareader role is identical to GRANT SELECT ON [database]. So it is still fine to use, but the recommendation is to move away from those roles to the more granular commands. Some of the other fixed database roles are less clearly defined for most people. Using the explicit commands results in greater clarity when reporting rights.

Obviously you know how to grant finer grained permissions. I am trying to break loose from the old roles whenever possible, but db_owner (for example) is a hard habit to break.

If all else fails read the documentation. Try here for starters (v. good diagram). In Oracle, a schema is a database. Also see here - particularly this:

One characteristic of an RDBMS is the independence of physical data storage from logical data structures. In Oracle Database, a database schema is a collection of logical data structures, or schema objects [i.e. related tables]. A database schema is owned by a database user and has the same name as the user name.

A further distinction is between the physical database files "the database" and the "instance" - the running software that makes up the fully working system.

In one sense, an Oracle "database" is useless - it's just a bunch of bits on a disk - it's the software which turns it into a system (i.e. a database in the sense that information is retrievable/modifiable).

An Oracle database is a running instance plus data (+ control + redo &c.) files which itself may contain 1 or many schemas which are themselves "databases" - i.e. as the layman would understand them - i.e. a HR, CRM or ERP (&...) schemas/systems.