Java Reference
In-Depth Information
The REVOKE command is used to revoke privileges granted to a user. Like the
GRANT command, REVOKE can be applied at various levels.
Users Groups and Roles
In addition to defining individual users, many systems also allow the database
administrator to organize users into logical groups with the same privileges. Like
users, user groups and roles are managed using SQL commands.
A database role defines what operations a user or group can do on the database,
such as "Create Databases," "Backup Databases," and so on. In other words, roles
are simply predefined sets of user privileges.
Creating, altering and dropping groups
Groups are created in much the same way as individual users. Groups are also
similar to individual users in that groups can be made part of other groups. When a
group is made a part of another group, it inherits the permissions of that group, along
with its own. In this way, you can create an entire hierarchy of groups and users and
manipulate them in accordance with your system needs.
When a group is altered or dropped, only the group is affected. Any users in a group
that is dropped simply lose their membership in the group. The users are otherwise
unaffected. Similarly, when a group is altered by dropping a user, only the group is
affected. The user simply loses his or her membership in the group but is otherwise
unaffected.
Creating roles
User roles
are simply a predefined set of user privileges. Most RDBMS systems
support the following roles or their equivalents:
Owner - A user who can read or write data and create, modify, and delete the database or its
components
Writer - A user allowed to read or write data
Reader - Someone allowed to read data but not write to the database
Public - The lowest possible status in terms of privileges
User roles are a neat administrative feature designed to save time for database
administrators. Like groups, roles can be defined by the database administrator as
required.
Database Architectures
