Averaging a list of TIMESTAMP(6) WITH TIME ZONE times - sql

Question

I've got 2 columns in a database of type TIMESTAMP(6) WITH TIME ZONE. I've subtracted one from the other to get the time between the two timestamps.
select lastprocesseddate-importeddate
from feedqueueitems
where eventid = 2213283
order by written desc;
How can I get an average of the list of time differences I have?
Here are a small sample of time differences:
+00 00:00:00.488871
+00 00:00:00.464286
+00 00:00:00.477107
+00 00:00:00.507042
+00 00:00:00.369144
+00 00:00:00.488918
+00 00:00:00.354797
+00 00:00:00.378801
+00 00:00:00.320040
+00 00:00:00.361242
+00 00:00:00.302327
+00 00:00:00.331441
+00 00:00:00.324065
EDIT: I also should have noted - I've tried the AVG function, and it just returns
ORA-00932: inconsistent datatypes: expected NUMBER got INTERVAL DAY TO SECOND
00932. 00000 - "inconsistent datatypes: expected %s got %s"
*Cause:
*Action:
Error at Line: 3 Column: 29
EDIT2: Just to clarify the above snippet. Line 3 is my SQL query all on one line in the following format:
select AVG(lastprocesseddate-importeddate) from feedqueueitems where eventid = 2213283;
EDIT3: Massive thanks to Matt and Alex Poole. You've both helped massively and I appreciate you taking the time to help with this and to both consistently return with updated help in response to the feedback/further problems! Thanks guys!

Answer 1

Use the AVG function
SELECT avg(cast(lastprocesseddate as date)-cast(importeddate as date))
FROM feedqueueitems
WHERE eventid = 2213283
ORDER BY written DESC;
On the Database with the +1 timezone for importeddate and lastprocesseddate is UTC
SELECT avg(cast(cast(lastprocesseddate as timestamp with time zone) at time zone '+01:00' as date)-cast(importeddate as date))
FROM feedqueueitems
WHERE eventid = 2213283
ORDER BY written DESC;

Answer 2

You could extract the time components from each gap value, which is an interval data type, so you end up with a figure in seconds (including the fractional part), and then average those:
select avg(extract(second from gap)
+ extract(minute from gap) * 60
+ extract(hour from gap) * 60 * 60
+ extract(day from gap) * 60 * 60 * 24) as avg_gap
from (
select lastprocesseddate-importeddate as gap
from feedqueueitems
where eventid = 2213283
);
A demo using a CTE to provide the interval values you showed:
with cte as (
select interval '+00 00:00:00.488871' day to second as gap from dual
union all select interval '+00 00:00:00.464286' day to second from dual
union all select interval '+00 00:00:00.477107' day to second from dual
union all select interval '+00 00:00:00.507042' day to second from dual
union all select interval '+00 00:00:00.369144' day to second from dual
union all select interval '+00 00:00:00.488918' day to second from dual
union all select interval '+00 00:00:00.354797' day to second from dual
union all select interval '+00 00:00:00.378801' day to second from dual
union all select interval '+00 00:00:00.320040' day to second from dual
union all select interval '+00 00:00:00.361242' day to second from dual
union all select interval '+00 00:00:00.302327' day to second from dual
union all select interval '+00 00:00:00.331441' day to second from dual
union all select interval '+00 00:00:00.324065' day to second from dual
)
select avg(extract(second from gap)
+ extract(minute from gap) * 60
+ extract(hour from gap) * 60 * 60
+ extract(day from gap) * 60 * 60 * 24) as avg_gap
from cte;
AVG_GAP
----------
.397544692
Or if you wanted it as an interval:
select numtodsinterval(avg(extract(second from gap)
+ extract(minute from gap) * 60
+ extract(hour from gap) * 60 * 60
+ extract(day from gap) * 60 * 60 * 24), 'SECOND') as avg_gap
...
which gives
AVG_GAP
--------------------
0 0:0:0.397544692
SQL Fiddle with answer in seconds. (It doesn't seem to like displaying intervals at the moment, so can't demo that).

Answer 3

This query should solve the issue.
WITH t AS
(SELECT
TIMESTAMP '2015-04-23 12:00:00.5 +02:00' AS lastprocesseddate,
TIMESTAMP '2015-04-23 12:05:10.21 UTC' AS importeddate
FROM dual)
SELECT
AVG(
EXTRACT(SECOND FROM SYS_EXTRACT_UTC(lastprocesseddate) - SYS_EXTRACT_UTC(importeddate))
+ EXTRACT(MINUTE FROM SYS_EXTRACT_UTC(lastprocesseddate) - SYS_EXTRACT_UTC(importeddate)) * 60
+ EXTRACT(HOUR FROM SYS_EXTRACT_UTC(lastprocesseddate) - SYS_EXTRACT_UTC(importeddate)) * 60 * 60
+ EXTRACT(DAY FROM SYS_EXTRACT_UTC(lastprocesseddate) - SYS_EXTRACT_UTC(importeddate)) * 60 * 60 * 24
) AS average_gap
FROM t;