考虑最近修改的日期取值

Question

I have the following columns where I need to take the most updated ID considering the most recent date an amendment has been made. For instance, I have used NVL(Updated_Date, Date) as Date, but am unsure of how to now take the ID that corresponds. The Code column is the one that I use to link to a separate table.

+--------------------------------------------+
| ID  |  DATE    |   UPDATED_DATE |   CODE   |
+--------------------------------------------+
| 123 | 1/2/2019 |                |   987    |
| 456 | 1/1/2019 |    2/4/2019    |   654    |
| 789 | 1/1/2019 |                |   654    |
+--------------------------------------------+

Ideally I would retrieve:

+----------------+
| ID  |   CODE   |
+----------------+
| 123 |   987    |
| 456 |   654    |
+----------------+

Many thanks in advance!

Answer 1

In Oracle, you can use aggregation and keep :

select code,
       min(id) keep (dense_rank first_value order by updated_date desc nulls lat) as id
from t
group by code;

Answer 2

Assuming you want the first row for each CODE which has the latest UPDATED_DATE then you can use the ROW_NUMBER() analytic function:

Oracle Setup :

CREATE TABLE table_name ( ID, "DATE", UPDATED_DATE, CODE ) AS
SELECT 123, DATE '2019-02-01', NULL,              987 FROM DUAL UNION ALL
SELECT 456, DATE '2019-01-01', DATE '2019-04-02', 654 FROM DUAL UNION ALL
SELECT 789, DATE '2019-01-01', NULL,              654 FROM DUAL;

Query :

SELECT ID, CODE
FROM   (
  SELECT t.*,
         ROW_NUMBER()
           OVER ( PARTITION BY code
                  ORDER BY UPDATED_DATE DESC NULLS LAST ) AS rn
  FROM   table_name t
)
WHERE rn = 1;

Output :

 ID | CODE --: | ---: 456 |  654 123 |  987 

db<>fiddle here