Problema con Natural Join y Jointure simple

[moginn]

Código MySQL:

SELECT t1.sessionDuration,
       t1.fullsession,
       mich_conversor(CAST(t2.Answered_Duration AS UNSIGNED)) AS Answered_Duration
FROM table1 t1 INNER JOIN table2 t2 ON t2.id_t1 = t1.id_t1;