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--Displays all of the open sessions and also displays the login name of the current user
select * from sys.dm_exec_sessions
select original_login()

--Returns size and fragmentation information for the data and indexes of the specified table or view in SQL Server.
select * from sys.dm_db_index_physical_stats (DB_ID(N'T1'), OBJECT_ID(N'ix_t1'), NULL, NULL , 'DETAILED')

sys.dm_exec_requests

--information about alerts that have been defined on the server
sp_help_alert