Compute average of data between time period in Oracle sql - sql

Question

I have the following table named IMETERDATA:
DEVNAME VARCHAR2(25)
DEVID VARCHAR2(8)
USEDATE TIMESTAMP(6)
INSTANTPOWER NUMBER(3,0)
TOTALENERGY NUMBER(7,4)
ROWNUMBER NUMBER(4,0)
I want to compute and show average of Totalenergy on 2-hour interval. For instance, if I have a data for specific date (e.g. Nov 22, 2016), I want to calculate average of Totalenergy for period of: 12am-2am, 2am-4am .... 10pm-12pm. I want to calculate the average for all dates with specified interval. What I have done so far:
select to_number(to_char(USEDATE, 'HH24')) as "HOUR",
avg(TOTALENERGY) as "AVERAGE", TRUNC(USEDATE, 'DD') as "DATE"
from IMETERDATA
WHERE TRUNC(USEDATE) in (select DISTINCT(TRUNC(USEDATE, 'DD'))
from IMETERDATA) and (to_number(to_char(USEDATE, 'HH24')) >= 12 and to_number(to_char(USEDATE, 'HH24')) < 14 )
group by to_number(to_char(USEDATE, 'HH24')), TRUNC(USEDATE, 'DD');
This query gives only average from 12pm to 2pm.How can I calculate for 24 hours? I want result from 12am to 11.59pm with interval of 2 hours:
12AM - 2AM ---> 58.50
2AM - 4AM ----> 60.35
...
10PM - 11.59PM --> 40.35

Answer 1

Hmm. Can I do it without creating another table?
Sure. Use a query like below (this example generates 2-hour periods for 2 days):
ALTER SESSION SET NLS_DATE_FORMAT = 'yyyy-mm-dd hh24:mi'
;
SELECT date '2016-11-22' + NUMTODSINTERVAL( 2 * (level - 1), 'HOUR' ) as period_start
FROM dual
CONNECT BY LEVEL <= 2 * 12 ; -- 2 days of 12 "two hours" periods
PERIOD_START
----------------
2016-11-22 00:00
2016-11-22 02:00
2016-11-22 04:00
2016-11-22 06:00
2016-11-22 08:00
2016-11-22 10:00
2016-11-22 12:00
2016-11-22 14:00
2016-11-22 16:00
2016-11-22 18:00
2016-11-22 20:00
2016-11-22 22:00
2016-11-23 00:00
2016-11-23 02:00
2016-11-23 04:00
2016-11-23 06:00
2016-11-23 08:00
2016-11-23 10:00
2016-11-23 12:00
2016-11-23 14:00
2016-11-23 16:00
2016-11-23 18:00
2016-11-23 20:00
2016-11-23 22:00
24 rows selected
And then join a result of the above query to your table and calculate averages
SELECT x.PERIOD_START,
AVG( i.TOTALENERGY )
FROM (
the_above_query
) x
JOIN IMETERDATA i
ON i.USEDATE >= x.PERIOD_START AND i.USEDATE < x.PERIOD_START + interval '2' hour
GROUP BY x.PERIOD_START

Answer 2

Have a look at Analytic Functions: windowing_clause, there you can do it straight forward.
select USEDATE,
AVG(TOTALENERGY) OVER (ORDER BY USEDATE RANGE BETWEEN INTERVAL '1' HOUR PRECEDING AND INTERVAL '1' HOUR FOLLOWING) as AVERAGE,
MIN(USEDATE) OVER (ORDER BY USEDATE RANGE BETWEEN INTERVAL '1' HOUR PRECEDING AND INTERVAL '1' HOUR FOLLOWING) as INTERVAL_START,
MAXUSEDATE) OVER (ORDER BY USEDATE RANGE BETWEEN INTERVAL '1' HOUR PRECEDING AND INTERVAL '1' HOUR FOLLOWING) as INTERVAL_END
from IMETERDATA;
This query gives you all averages for each time +/- 1 hour (i.e. 2 hours).
If you need just the times of given hours you can use
with t as
(select USEDATE,
AVG(TOTALENERGY) OVER (ORDER BY USEDATE RANGE BETWEEN INTERVAL '1' HOUR PRECEDING AND INTERVAL '1' HOUR FOLLOWING) as AVERAGE,
MIN(USEDATE) OVER (ORDER BY USEDATE RANGE BETWEEN INTERVAL '1' HOUR PRECEDING AND INTERVAL '1' HOUR FOLLOWING) as INTERVAL_START,
MAXUSEDATE) OVER (ORDER BY USEDATE RANGE BETWEEN INTERVAL '1' HOUR PRECEDING AND INTERVAL '1' HOUR FOLLOWING) as INTERVAL_END
from IMETERDATA)
select *
from t
where USEDATE = TRUNC(USEDATE, 'HH')
AND EXTRACT(HOUR FROM USEDATE) IN (1,3,5,7,...);
Instead of EXTRACT(HOUR FROM USEDATE) IN (1,3,5,7,...) you could also use MOD(EXTRACT(HOUR FROM USEDATE), 1) = 1
Maybe this is not 100% what you are looking for (your question is not so clear in that regards) but I assume you get an idea how to use it.