SELECT sys.ps_thread_id(234623462376);
sys.ps_thread_id(234623462376)
NULL
SELECT sys.ps_thread_id(CONNECTION_ID()) = @ps_thread_id;
sys.ps_thread_id(CONNECTION_ID()) = @ps_thread_id
1
SELECT sys.ps_thread_id(NULL) = @ps_thread_id;
sys.ps_thread_id(NULL) = @ps_thread_id
1