SQL Server server and database default roles

Server roles:
Described in order from the lowest-level role (bulkadmin) to the highest-level role (sysadmin):
1.bulkadmin: This role can run the BULK INSERT statement. This statement allows data to be imported from a text file into the SQL Server2008 database, and is designed for domain accounts that need to be bulk inserted into the database.
2.dbcreator: This role can create, change, delete, and restore any database. Not only for the Assistant DBA role, but also for the developer role.
3.diskadmin: This role is used to manage disk files, such as mirror databases and add backup devices. Suitable for assistant DBA
4.processadmin:sql Server 2008 can process multiple processes at the same time. This role can end a process (called "delete" in SQL Server 2008)
5.public: There are two major features: first, there is no permission in the initial state; second, all database users are members of it.
6.securityadmin: This role will manage logins and their properties. You can authorize, deny, and REVOKE server-level/database-level permissions. You can reset the login name and password
7.serveradmin: This role can change server-wide configuration options and shut down the server
8.setupadmin: Designed for users who need to manage join servers and control the stored procedures that are started.
9.sysadmin: This role has the right to perform any operation in SQL Server 2008.
 
Database roles:
1.db_accessadmin: Database users, groups and roles can be added and removed from the database
2.db_backupoperator: Can back up the database
3.db_datareader can read data from any table
4.db_datawriter can add, change, or delete data from all tables
5.db_ddladmin can add, change, or delete database objects (that is, any DDL statements can be executed)
6.db_denydatareader cannot read data from any table, but can still view it through stored procedures
7.db_denydatawriter cannot change data in any table, but can still modify it through stored procedures
8.db_owner perform any action
9.db_securityadmin can change permissions and roles in the data
10.public: Each database user belongs to the public role. The user is granted permission to the public role before the user is authorized. The role cannot be deleted

SQL Server server and database default roles