In order to manage permissions on a database easily, SQL Sever provides following Fixed database roles:
1)db_owner : This role perform all configuration and maintenance activities on the database, and can also drop the database.
2)db_securityadmin : This role can modify role membership and manage permissions. Adding principals to this role could enable unintended privilege escalation.
3)db_accessadmin : This role can add or remove access to the database for Windows logins, Windows groups, and SQL Server logins.
4)db_backupoperator : This role can back up the database.
5)db_ddladmin : This role can run any DDL command on a database.
6)db_datawriter : This role can add, delete, or change data in all user tables.
7) db_datareader : This role can read all data from all user tables.