Query for selecting distinct by date

Question

Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
I have a simple table that has an ID, Title, and Date.
I need to select the most recent ID (without duplicates). I was looking at using a UNION but couldn't quite get it to work.
P3XGL2FV96     Test 1     11-AUG-10 03.38.06.000000000 PM
1VGJ74PSNW     Test 2     11-AUG-10 04.02.22.000000000 PM
1VGJ74PSNW     Test 2     12-AUG-10 09.49.09.000000000 AM

Answer 1

Hi,
You could achieve it like this :
CREATE TABLE MY_TABLE
+(+
ID       VARCHAR2(10),
TITLE    VARCHAR2(10),
MY_DATE TIMESTAMP
+);+
insert into my_table values ('P3XGL2FV96', 'Test 1', '11-AUG-10 03.38.06.000000000 PM');
insert into my_table values ('1VGJ74PSNW', 'Test 2', '12-AUG-10 09.49.09.000000000 AM');
insert into my_table values ('1VGJ74PSNW', 'Test 2', '11-AUG-10 04.02.22.000000000 PM');
commit;
SELECT id, title, my_date
FROM (SELECT id,
title,
my_date,
RANK () OVER (PARTITION BY id ORDER BY my_date DESC) rk
FROM my_table)
WHERE rk = 1;
ID        |TITLE     |MY_DATE
----------|----------|---------------------------------------------------------------------------
+1VGJ74PSNW|Test 2 |12-AUG-10 09.49.09.000000 AM+
P3XGL2FV96|Test 1    |11-AUG-10 03.38.06.000000 PM
Remark : if one id have twice the same date they will be both ranked first
Kind regards,
Ludovic
Edited by: ludovic.sz on Aug 12, 2010 8:38 AM