Get records with max value on grouped SQL results (mysql)
You can get max(created_dt) of each conversation and then join it with main table in this way:




select   tbl.*
from     tbl
join     (select   conversation_id, max(created_dt) created_dt
          from     tbl
          group by conversation_id) t1
on       tbl.conversation_id = t1.conversation_id
and      tbl.created_dt = t1.created_dt;



id | member_a_id | member_b_id | conversation_id | created_dt          | content
-: | ----------: | ----------: | --------------: | :------------------ | :------
 3 |         105 |         100 |               2 | 2018-04-01 14:00:00 | ccc    
 5 |         100 |         110 |               1 | 2018-04-01 16:00:00 | eee    



db&lt;>fiddle here