MYSQL JOIN and get full row based on MAX

Question

Really tried to search for a solution to this, but I can't get it to work. I have 2 tables in Mysql event_parties and events .

event_parties:
g_event_id   agent_id
----------   --------
2917         2
2918         2
2919         2
3067         3
3078         3

events:
g_event_id   event_id   event_time
----------   --------   ----------
2917         29         2016-10-19 15:24:25
2918         31         2016-10-19 15:24:28
2919         30         2016-10-19 15:29:46
3067         29         2016-10-20 15:33:46
3078         30         2016-10-21 15:29:46

I need an JOIN between these two tables with g_event_id as the ID. I need all fields in table events and I need the row with highest g_event_id or with highest event_time .

Like this:

agent_id   g_event_id   event_id   event_time
--------   ----------   --------   ----------
2          2919         30         2016-10-19 15:29:46
3          3078         30         2016-10-21 15:29:46

Been struggling with this for several days :(

/ Kristian

Answer 1

For just the one highest: ORDER BY g_event_id DESC, event_time DESC LIMIT 1

UPDATE:

for highest per something, you need a double join. first have all in one table, and then join in later, and the one row that don't have a later evetn, is the latests event.

for g_event_id as definition of later

SELECT event_parties.agent_id, event_parties.g_event_id, event_id, event_time
FROM event_parties
INNER JOIN events USING (g_event_id)
LEFT JOIN event_parties AS later_event
   ON (later_event.agent_id = event_parties.agent_id 
      AND later_event.g_event_id > event_parties.g_event_id)
WHERE later_event.g_event_id IS NULL
GROUP BY event_parties.agent_id

Answer 2

try this:

select 
ep.agent_id,
ep.g_event_id,
e.event_id,
e.event_time
from event_parties ep
join events e on e.g_event_id = ep.g_event_id
order by e.g_event_id DESC, e.event_time desc
limit 1