Closest date/time to top of hour - oracle

Question

I have a table with normal DATE field in it:
5/9/2022 2:32:02 AM
5/9/2022 12:33:02 PM
5/9/2022 10:34:02 AM
5/9/2022 10:20:02 AM
5/9/2022 6:54:02 AM
5/9/2022 4:28:02 AM
5/9/2022 5:08:02 AM
I need a query that I can run that will give me the record that is the closest to the top of the hour I am asking for. So like, which is closest to 5:00am, or 7:00am, or 12:00pm.
Thanks!

Answer 1

A query like the one below can be used to show each record that is closest to the "top of the hour". In your sample data, none of the records overlap to the nearest "top of the hour", so all the records will be shown. If you add additional dates that are closer together to the top of the hour, then only the the dates closest to the "top of the hour" will be shown.
Query
WITH
sample_dates (dt)
AS
(SELECT TO_DATE ('5/9/2022 2:32:02 AM', 'MM/DD/YYYY HH:MI:SS PM') FROM DUAL
UNION ALL
SELECT TO_DATE ('5/9/2022 12:33:02 PM', 'MM/DD/YYYY HH:MI:SS PM') FROM DUAL
UNION ALL
SELECT TO_DATE ('5/9/2022 10:34:02 AM', 'MM/DD/YYYY HH:MI:SS PM') FROM DUAL
UNION ALL
SELECT TO_DATE ('5/9/2022 10:20:02 AM', 'MM/DD/YYYY HH:MI:SS PM') FROM DUAL
UNION ALL
SELECT TO_DATE ('5/9/2022 6:54:02 AM', 'MM/DD/YYYY HH:MI:SS PM') FROM DUAL
UNION ALL
SELECT TO_DATE ('5/9/2022 4:28:02 AM', 'MM/DD/YYYY HH:MI:SS PM') FROM DUAL
UNION ALL
SELECT TO_DATE ('5/9/2022 5:08:02 AM', 'MM/DD/YYYY HH:MI:SS PM') FROM DUAL)
SELECT TO_CHAR (dt, 'MM/DD/YYYY HH:MI:SS PM') AS dt,
TO_CHAR (nearest_hour, 'MM/DD/YYYY HH:MI:SS PM') AS nearest_hour
FROM (SELECT dt,
nearest_hour,
ROW_NUMBER () OVER (PARTITION BY nearest_hour ORDER BY time_from_hour) AS time_rank
FROM (SELECT dt,
CASE
WHEN dt - TRUNC (dt, 'HH') <
ABS ((TRUNC (dt, 'HH') + INTERVAL '1' HOUR) - dt)
THEN
TRUNC (dt, 'HH')
ELSE
TRUNC (dt, 'HH') + INTERVAL '1' HOUR
END AS nearest_hour,
LEAST (dt - TRUNC (dt, 'HH'),
ABS ((TRUNC (dt, 'HH') + INTERVAL '1' HOUR) - dt)) AS time_from_hour
FROM sample_dates))
WHERE time_rank = 1
ORDER BY 1;
Result
DT NEAREST_HOUR
_________________________ _________________________
05/09/2022 02:32:02 AM 05/09/2022 03:00:00 AM
05/09/2022 04:28:02 AM 05/09/2022 04:00:00 AM
05/09/2022 05:08:02 AM 05/09/2022 05:00:00 AM
05/09/2022 06:54:02 AM 05/09/2022 07:00:00 AM
05/09/2022 10:20:02 AM 05/09/2022 10:00:00 AM
05/09/2022 10:34:02 AM 05/09/2022 11:00:00 AM
05/09/2022 12:33:02 PM 05/09/2022 01:00:00 PM

Answer 2

To get the closest row to a particular hour on any day then, from Oracle 12, you can use:
SELECT *
FROM table_name
ORDER BY ABS(
TRUNC(yourDate) + INTERVAL '07:00:00' HOUR TO SECOND
- yourDate
)
FETCH FIRST ROW ONLY;
Which, for the sample data:
CREATE TABLE table_name (id, yourDate) AS
SELECT 1, DATE '2022-05-09' + INTERVAL '02:32:02' HOUR TO SECOND FROM DUAL UNION ALL
SELECT 2, DATE '2022-05-09' + INTERVAL '12:33:02' HOUR TO SECOND FROM DUAL UNION ALL
SELECT 3, DATE '2022-05-09' + INTERVAL '10:34:02' HOUR TO SECOND FROM DUAL UNION ALL
SELECT 4, DATE '2022-05-09' + INTERVAL '10:20:02' HOUR TO SECOND FROM DUAL UNION ALL
SELECT 5, DATE '2022-05-09' + INTERVAL '06:54:02' HOUR TO SECOND FROM DUAL UNION ALL
SELECT 6, DATE '2022-05-09' + INTERVAL '04:28:02' HOUR TO SECOND FROM DUAL UNION ALL
SELECT 7, DATE '2022-05-09' + INTERVAL '05:08:02' HOUR TO SECOND FROM DUAL;
Outputs:
ID
YOURDATE
5
2022-05-09 06:54:02
If you want the closest hour to each of your rows then:
SELECT t.*,
TRUNC(yourDate, 'HH') + ROUND((yourDate - TRUNC(yourDate, 'HH'))*24)/24
AS nearest_hour
FROM table_name t
Outputs:
ID
YOURDATE
NEAREST_HOUR
1
2022-05-09 02:32:02
2022-05-09 03:00:00
2
2022-05-09 12:33:02
2022-05-09 13:00:00
3
2022-05-09 10:34:02
2022-05-09 11:00:00
4
2022-05-09 10:20:02
2022-05-09 10:00:00
5
2022-05-09 06:54:02
2022-05-09 07:00:00
6
2022-05-09 04:28:02
2022-05-09 04:00:00
7
2022-05-09 05:08:02
2022-05-09 05:00:00
If, for each closest hour, you want the single closest row then:
SELECT *
FROM (
SELECT t.*,
ROW_NUMBER() OVER (PARTITION BY nearest_hour ORDER BY ABS(nearest_hour - yourDate))
AS rn
FROM (
SELECT t.*,
TRUNC(yourDate, 'HH') + ROUND((yourDate - TRUNC(yourDate, 'HH'))*24)/24
AS nearest_hour
FROM table_name t
) t
)
WHERE rn = 1
Outputs:
ID
YOURDATE
NEAREST_HOUR
RN
1
2022-05-09 02:32:02
2022-05-09 03:00:00
1
6
2022-05-09 04:28:02
2022-05-09 04:00:00
1
7
2022-05-09 05:08:02
2022-05-09 05:00:00
1
5
2022-05-09 06:54:02
2022-05-09 07:00:00
1
4
2022-05-09 10:20:02
2022-05-09 10:00:00
1
3
2022-05-09 10:34:02
2022-05-09 11:00:00
1
2
2022-05-09 12:33:02
2022-05-09 13:00:00
1
db<>fiddle here