PL-SQL query to find the most recent record the "Operation_date" of which is lower than a specified date

Question

I have a table with below structure:

create table DOC_AMOUNT_DETAIL
(
  col_id         NUMBER,
  amount         NUMBER,
  operation_date DATE      
)

some example data for this table is :

col_id    |  amount   |  operation_date 
---------------------------------------
  1       |  5000     |  11/1/2020  
  2       |  1000     |  11/1/2020 
  3       |  3000     |  11/1/2020     
  1       |  1000     |  11/14/2020
  2       |   500     |  11/14/2020

If the amount column of each col_id changes , a new record will be inserted in the table with a new operation_date which is exactly the date of the change. What I need from the table is the amount for each col_id which has the max(operation_date)<= (a specific date for example 11/15/2020) by this I mean I need the last update of the record the operation_date of which is lower than the date I'm querying the table. So my desired result is this :

    col_id    |  amount   
    --------------------
      1       |  1000      
      2       |  500    
      3       |  3000       

What I've written so far is this and it gives me the correct output:

select d.col_id, 
       d.amount
  from doc_amount_detail d
 inner join (select t.col_id, 
             max(t.operation_date) operation_date
               from doc_amount_detail t
              where t.operation_date <= to_date('11/15/2020', 'mm/dd/yyyy')
              group by t.col_id
             ) d2
    on d.col_id = d2.col_id
   and d.operation_date = d2.operation_date

and I want to know whether there are better ways of writing this query. Thanks in advance.

Answer 1

Analytic Functions

select
  col_id, amount
from
 (
   select
     d.col_id, d.amount,
     rank() over (partition by d.col_id order by d.operation_date desc) as rk
   from doc_amount_detail d
   where.d.operation_date <= to_date('11/15/2020', 'mm/dd/yyyy')
 )
where rk = 1; 

Answer 2

I found a better solution. Instead of Last_value() function , I used First_value() and order by t.operation_date desc:

select distinct 
       t.col_id,
       first_value(t.amount) over(partition by t.col_id order by t.operation_date desc ) amount
from doc_amount_detail t
where t.operation_date <= to_date('11/15/2020', 'mm/dd/yyyy');