Datepart function in oracle - oracle

Question

I have some sample records in Oracle 12
Date_Time Item
10/1/2012 12:05:00 AM 3
12/3/2012 06:00:00 AM 2
11/8/2012 14:05:05 PM 10
12/9/2012 16:00:59 PM 5
I like to aggregate the Item field based on military time or in three different times: 00:00:00AM to 05:59:00AM, 06:00:00AM to 15:59:00PM, and 16:00:00PM to 23:59:00PM. I was able to use the Datepart function in SQL to do this. I was wondering what function in Oracle 12 that allows me to count the Item between these three different times.
My desired output would be:
Date_Time Count
00:00:00AM to 05:59:00AM = 3
06:00:00AM to 15:59:00PM = 12
16:00:00PM to 23:59:00PM = 5

Answer 1

In oracle, date datatype contains date+time ,so you just need just use group by
SELECT Date_Time, COUNT(*) item FROM YOUR_TABLES
GROUP BY Date_Time;
NEW Answer:
SELECT TO_CHAR(DATE_TIME,'HH24') time, count(*) FROM YOUR_TABLE
WHERE TO_CHAR(DATE_TIME,'HH24') >= '00'
AND TO_CHAR(DATE_TIME,'HH24') < '06'
GROUP BY TO_CHAR(DATE_TIME,'HH24')
UNION ALL
SELECT TO_CHAR(DATE_TIME,'HH24') time, count(*) FROM YOUR_TABLE
WHERE TO_CHAR(DATE_TIME,'HH24') >= '06'
AND TO_CHAR(DATE_TIME,'HH24') < '16'
GROUP BY TO_CHAR(DATE_TIME,'HH24')
UNION ALL
SELECT TO_CHAR(DATE_TIME,'HH24') time, count(*) FROM YOUR_TABLE
WHERE TO_CHAR(DATE_TIME,'HH24') >= '16'
AND TO_CHAR(DATE_TIME,'HH24') < '00'
GROUP BY TO_CHAR(DATE_TIME,'HH24');
and if your table is huge :
first :partition it
second: create local functional index on TO_CHAR(DATE_TIME,'HH24:MI:SS')

Answer 2

Assuming that date_time column is datatype DATE, we can use the TO_CHAR function to extract a two character representation... in the range 00 to 23.
(The selected answer demonstrates this approach to extracting the "hour" from an Oracle DATE.)
Assuming that we want every non-null time value to fall into one of three time ranges... that is, if we don't want any of time values to be omitted because of a crack/gap in between the ranges, and we don't want any overlap in the ranges...
We can use a simple "less than" tests in a CASE expression.
Consider a time close to a boundary: '05:59:33'. That's after 05:59:00 but before 06:00:00. If we want that included in the first range, we can just test for hour < '06'.
If was grouping the rows into three ranges, and I wanted a total of the item column, I'd do something like this:
SELECT CASE
WHEN TO_CHAR( t.date_time ,'HH24') < '06' THEN '00:00:00 to 05:59:59'
WHEN TO_CHAR( t.date_time ,'HH24') < '16' THEN '06:00:00 to 15:59:59'
WHEN TO_CHAR( t.date_time ,'HH24') < '24' THEN '16:00:00 to 23:59:59'
END AS time_range
, SUM(t.item)
FROM mytable t
GROUP
BY CASE
WHEN TO_CHAR( t.date_time ,'HH24') < '06' THEN '00:00:00 to 05:59:59'
WHEN TO_CHAR( t.date_time ,'HH24') < '16' THEN '06:00:00 to 15:59:59'
WHEN TO_CHAR( t.date_time ,'HH24') < '24' THEN '16:00:00 to 23:59:59'
END
and add an ORDER BY clause if I want the results returned in a particular order.
If the table contains any NULL values of date_time, the query above will also return a fourth time_range with a NULL value.

Answer 3

Here is how you would get the desired result in three columns (rather than three rows), which makes more sense for most applications. You can change this easily to get the result in rows instead.
Note that if dt is any date in Oracle, dt - trunc(dt) is the number of days (a fraction with value less than 1) since midnight.
select sum(case when dt-trunc(dt) < 6/24 then item else 0 end) as morning,
sum(case when dt-trunc(dt) >= 6/24
and dt-trunc(dt) < 16/24 then item else 0 end) as daytime,
sum(case when dt-trunc(dt) >= 16/24 then item else 0 end) as evening
from your_table
;