SQL Server SPID

Viewing SPIDs

-- All SPID
SELECT * FROM sys.dm_exec_sessions

-- SPID for your current execution window
SELECT @@SPID

Blocking

sp_who2

SPID Status

SELECT
	SPID = er.session_id
	,Status = ses.status
	,[Login] = ses.login_name
	,Host = ses.host_name
	,BlkBy = er.blocking_session_id
	,DBName = DB_Name(er.database_id)
	,CommandType = er.command
	,SQLStatement = st.text
	,ObjectName = OBJECT_NAME(st.objectid)
	,ElapsedMS = er.total_elapsed_time
	,CPUTime = er.cpu_time
	,IOReads = er.logical_reads + er.reads
	,IOWrites = er.writes
	,LastWaitType = er.last_wait_type
	,StartTime = er.start_time
	,Protocol = con.net_transport
	,ConnectionWrites = con.num_writes
	,ConnectionReads = con.num_reads
	,ClientAddress = con.client_net_address
	,Authentication = con.auth_scheme
FROM 
	sys.dm_exec_requests er
	OUTER APPLY sys.dm_exec_sql_text(er.sql_handle) st
	LEFT JOIN sys.dm_exec_sessions ses ON ses.session_id = er.session_id
	LEFT JOIN sys.dm_exec_connections con ON con.session_id = ses.session_id

Sources:

SQL Server SPID – What is it?