gistfile1.txt

     person    |      version     |       date       |      created_at      |             data
       1       |         1        |    01/01/2019    |      05/08/2019      |             null
       2       |         1        |    01/01/2019    |      05/08/2019      |             null
       1       |         1        |    02/01/2019    |      05/08/2019      |             null
       2       |         1        |    02/01/2019    |      05/08/2019      |             null
       1       |         2        |    01/01/2019    |      06/08/2019      |          "some data"
       1       |         3        |    01/01/2019    |      06/08/2019      |      "some altered data"
       1       |         3        |    01/01/2019    |      05/08/2019      |      "also altered data"
       
       
       
       
/* 
DESIRED RESULT 
I want to select the data for all different persons and dates at the highest versions and highest created at.
It is possible for the same person, data and version to co-exists (the created at will never be the same in this case)
*/


(person 1, date 01/01/2019, "some altered data")
(person 1, date 02/01/2019, null)
(person 2, date 01/01/2019, null)
(person 2, date 02/01/2019, null)

select dpr.person, dpr.date, dpr.data from table dpr
inner join (
select dpr1.person, dpr1.date, max(created_at) as mostrecent
from table dpr1
inner join
(SELECT
dpr.person, dpr.date, max(dpr.version) as maxversion
FROM
table dpr
GROUP BY
person, date) as dpr2
ON dpr1.person = dpr2.person AND dpr1.date = dpr2.date AND dpr1.version = dpr2.maxversion
group by dpr1.person, dpr1.date
) as dpr2
ON dpr.person = dpr2.person AND dpr.date = dpr2.date AND dpr.created_at = dpr2.mostrecent
ORDER BY dpr.person, dpr.date;