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

Answer 2

Try this query :-

select * from (
select * from (
SELECT     a.id, 
           nia.idaction grp_is, 
           MAX(CONCAT(nia.fecha, ' ', nia.hora)) time_is
FROM       nectar_incidencias_alarma nia 
INNER JOIN alarmas a 
        ON a.id=nia.id_alarma 
WHERE      nia.idaction IN (6,7) 
GROUP BY   a.id
) tab1
order by tab1.time_is desc) tab2
group by tab2.grp_is