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SQL Server: fixed database roles

There are nine fixed database roles:
db_accessadmin
db_backupoperator
db_datareader
db_datawriter
db_ddladmin
db_denydatareader
db_denydatawriter
db_owner
db_securityadmin
These roles can be found with the following SQL statement; 
select
   name
from
   sys.database_principals
where
   is_fixed_role = 1
order by
   name;

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