Checking query duration using the sys.dm_exec_requests dmv

Hi,

I've tried to use this query after the execution of the statement SELECT * FROM mytable:

SELECT 
    session_id,
    status,
    start_time,
    command,
    sql_handle,
    plan_handle,
    database_id,
    blocking_session_id,
    wait_type,
    wait_time,
    wait_resource,
    last_wait_type,
    cpu_time,
    total_elapsed_time,
    reads,
    writes,
    logical_reads,
    text
FROM 
    sys.dm_exec_requests AS r
CROSS APPLY 
    sys.dm_exec_sql_text(r.sql_handle) AS t
WHERE 
    t.text = 'SELECT * FROM mytable';

but no rows are returned.

Perhaps the query is wrong.

Any suggests to me in order to checking the execution time of an user query? Thanks