Select newest data from id A

Question

I have the data like this:

ID  TRANS_ID  CREATED_DATE             STATUS
----------------------------------------------
1   AA        2017-05-19 02:00:00      WAITING
2   AA        2017-05-20 02:00:00      IN_PROCESS
3   BB        2017-05-19 02:00:00      WAITING
4   CC        2017-05-19 02:00:00      WAITING
5   CC        2017-05-20 02:00:00      IN_PROCESS

I would like to show the data in table view like this one :

ID  TRANS_ID  CREATED_DATE             STATUS
----------------------------------------------
2   AA        2017-05-20 02:00:00      IN_PROCESS
3   BB        2017-05-19 02:00:00      WAITING
5   CC        2017-05-20 02:00:00      IN_PROCESS

I take the newest data from each trans_id and I run this query but it does not work

select id, max(created_date), trans_id, status
from table_a
group by a.transaction_id

Answer 1

One option is to filter with a correlated subquery:

select t.*
from mytable t
where t.created_date = (
    select max(t1.created_date) from mytable t1 where t1.trans_id = t.trans_id
)

Alternatively, you can use window functions:

select id, trans_id, created_date, status
from (
    select t.*, rank() over(partition by trans_id order by created_date desc) rn
    from mytable t
) t
where rn = 1

This allows top ties, if any. If you want no ties, you can use row_number() instead of rank().