Getting rows filtered by most recent time mysql

Question

I have a question of a complex query and I don\'t know how to write it. I have the next table:

+---------------+-----------+----------+--------------------------         


        

Answer 1

To retrieve the correct value of idaction, you could use group_concat in combination with substring_index. Note that you don't really need to join the table alarmas, as you have all you need in nectar_incidencias_alarma:

SELECT     id_alarma,
           SUBSTRING_INDEX(GROUP_CONCAT(idaction 
                           ORDER BY CONCAT(fecha, ' ', hora) DESC), ',', 1)+0 id_action,
           MAX(CONCAT(fecha, ' ', hora)) 
FROM       nectar_incidencias_alarma
WHERE      idaction IN (6,7) 
GROUP BY   id_alarma