Query to find the blocking session

How do we find the session that is causing a deadlock?

The following query will help us find what session is causing deadlock:

select session_id,start_time,[status],command,blocking_session_id,wait_time, 
open_transaction_count,transaction_id,total_elapsed_time, definition=cast(text as varchar(max))
from sys.dm_exec_requests
cross apply sys.dm_exec_sql_text(sql_handle) where blocking_session_id!=0