SQL Server Fixed Database-Level Roles

Fixed database roles are defined at the database level and exist in each database. Members of the db_owner and db_securityadmin database roles can manage fixed database role membership; however, only members of the db_owner database role can add members to the db_owner fixed database role.

The fixed database roles are the following:
* db_accessadmin
* db_backupoperator
* db_datareader
* db_datawriter
* db_ddladmin

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