PostgreSQL getting latest record in function

Question

I have got function named cdr_get_call_log. I m getting my data from this function. As you see in example data record number 3 and 4 is got same source_caller_id and same day but different time. So i want if there are same source_caller_id in my data i want to get only record that start_time is latest

select source_caller_id,destination_dn,recording_url,start_time 
from (
  select * 
  from cdr_get_call_log
  where destination_type=0 
    and talking_duration is not null 
    and source_caller_id not like 'Ext%' 
    and source_caller_id like '0%' 
    and destination_dn in('628','627','629','630','631','626','600','632') 
    and source_caller_id<> '09903114243' 
    and subrow_desc_number='1' 
    and trim(recording_url)<> ''
) as a

Table Structure

| source_caller_id | destination_dn |   recording_url    |      start_time       |
|------------------|----------------|--------------------|-----------------------|
|    1.05356785544 |            627 | [627]/20180230.wav | 01/12/2018 11.12:39   |
|    2.05551165244 |            632 | [632]/20180230.wav | 04/12/2018 09.12:39   |
|    3.05556665544 |            621 | [627]/20180230.wav | 06/12/2018 05.12:39   |
|    4.05556665544 |            626 | [627]/20180230.wav | 06/12/2018 05.15:39   |

Answer 1

You can use distinct on:

with q as (<your query here>)
select distinct on (caller_id, date_trunc('day', start_time)) q.*
from q
order by caller_id, date_trunc('day', start_time), start_time desc;