ALTER ROLE (Transact-SQL)
Adds members to a database role or changes the name of a user-defined database role.
Changing the name of a database role does not change ID number, owner, or permissions of the role.
Database roles are visible in the sys.database_role_members and sys.database_principals catalog views.
Beginning with SQL Server 2005, the behavior of schemas changed. As a result, code that assumes that schemas are equivalent to database users may no longer return correct results. Old catalog views, including sysobjects, should not be used in a database in which any of the following DDL statements have ever been used: CREATE SCHEMA, ALTER SCHEMA, DROP SCHEMA, CREATE USER, ALTER USER, DROP USER, CREATE ROLE, ALTER ROLE, DROP ROLE, CREATE APPROLE, ALTER APPROLE, DROP APPROLE, ALTER AUTHORIZATION. In such databases you must instead use the new catalog views. The new catalog views take into account the separation of principals and schemas that was introduced in SQL Server 2005. For more information about catalog views, see Catalog Views (Transact-SQL).
A. Changing the Name of a Database Role
The following example changes the name of role buyers to purchasing.