Detailed explanation of server roles and database role permissions in SQL Server

Fixed database role description
db_owner
User who can perform all technical actions in the database db_accessadmin User who can add and delete users
db_datareader User who can view data in user tables in all databases
db_datawriter User who can add, modify or delete data in user tables in all databases db_ddladmin A user who can
perform all DDL operations in the database
db_securityadmin A user
who can manage all actions related to security permissions in the database
db_backoperator A user who
can back up the database (and can issue DBCC and CHECKPOINT
statements , which are generally executed before the backup. Execute)
db_denydatareader User who cannot see any data in the database db_denydatawriter User who cannot change any data in the database The

sa login is the login of the system administrator. Roles did not exist in previous SQL Server versions, and the sa login had all possible permissions for system administration work. In SQL Server 2005, the sa login maintains backward compatibility. The sa login is always a member of the fixed server role syadmin and cannot be removed from this role.

Note: Use the sa login only if there is no other way to log in to the SQL Server system.