How do I get the latest records from every customer with a time delta

I want to get the most recent records for every customer and also accept/get records which are 1 hour older to the most recent record.

I am currently getting the most recent records for every customer using this SQL query –

SELECT sub.customer, sub.date_field  FROM(
        SELECT  customer, date_field,
                RANK() OVER
                (
                    PARTITION by customer
                    ORDER BY date_field desc
                ) AS rownum 
        FROM TableA) sub 
WHERE rownum = 1 

What I need is to get the most recent records and records which are an hour older than the recent records for every customer.

Answer

Hmmm . . . You can get the maximum timestamp and use date comparisons:

select a.*
from (select a.*,
             max(timestamp) over (partition by customer) as max_timestamp
      from tableA a
     ) a
where timestamp >= max_timestamp - interval '1 hour'
order by customer, timestamp desc;