Count the number of 7AM or 7PM occurrences between two datetimes - sql

Question

Is there an easy way to do this? By fully between, I mean don't count the 7am or 7pm datetimes that are equal to the start or end time.
I imagine this can be done using the unix timestamp in seconds and a bit of algebra, but I can't figure it out.
I'm happy to use something in PLSQL or plain SQL.
Examples:
start end num_7am_7pm_between_dates
2012-06-16 05:00 2012-06-16 08:00 1
2012-06-16 16:00 2012-06-16 20:00 1
2012-06-16 05:00 2012-06-16 07:00 0
2012-06-16 07:00 2012-06-16 19:00 0
2012-06-16 08:00 2012-06-16 15:00 0
2012-06-16 05:00 2012-06-16 19:01 2
2012-06-16 05:00 2012-06-18 20:00 6

Answer 1

I think this could be reduced further but I don't have Oracle at my disposal to completely test this Oracle SQL:
SELECT StartDate
, EndDate
, CASE WHEN TRUNC(EndDate) - TRUNC(StartDate) < 1
AND TO_CHAR(EndDate, 'HH24') > 19
AND TO_CHAR(StartDate, 'HH24') < 7
THEN 2
WHEN TRUNC(EndDate) - TRUNC(StartDate) < 1
AND (TO_CHAR(EndDate, 'HH24') > 19
OR TO_CHAR(StartDate, 'HH24') < 7)
THEN 1
WHEN TRUNC(EndDate) - TRUNC(StartDate) > 0
AND TO_CHAR(EndDate, 'HH24') > 19
AND TO_CHAR(StartDate, 'HH24') < 7
THEN 2 + ((TRUNC(EndDate) - TRUNC(StartDate)) * 2)
WHEN TRUNC(EndDate) - TRUNC(StartDate) > 0
AND TO_CHAR(EndDate, 'HH24') > 19
OR TO_CHAR(StartDate, 'HH24') < 7
THEN 1 + ((TRUNC(EndDate) - TRUNC(StartDate)) * 2)
ELSE 0
END
FROM MyTable;
Thanks to #A.B.Cade for the Fiddle, it looks like my CASE Logic can be condensed further to:
SELECT SDate
, EDate
, CASE WHEN TO_CHAR(EDate, 'HH24') > 19
AND TO_CHAR(SDate, 'HH24') < 7
THEN 2 + ((TRUNC(EDate) - TRUNC(SDate)) * 2)
WHEN TO_CHAR(EDate, 'HH24') > 19
OR TO_CHAR(SDate, 'HH24') < 7
THEN 1 + ((TRUNC(EDate) - TRUNC(SDate)) * 2)
ELSE 0
END AS MyCalc2
FROM MyTable;

Answer 2

I had fun writing the following solution:
with date_range as (
select min(sdate) as sdate, max(edate) as edate
from t
),
all_dates as (
select sdate + (level-1)/24 as hour
from date_range
connect by level <= (edate-sdate) * 24 + 1
),
counts as (
select t.id, count(*) as c
from all_dates, t
where to_char(hour, 'HH') = '07'
and hour > t.sdate and hour < t.edate
group by t.id
)
select t.sdate, t.edate, nvl(counts.c, 0)
from t, counts
where t.id = counts.id(+)
order by t.id;
I added an id column to the table in case the range of dates aren't unique.
http://www.sqlfiddle.com/#!4/5fa19/13

Answer 3

This may not have the best performance but might work for you:
select sdate, edate, count(*)
from (select distinct edate, sdate, sdate + (level / 24) hr
from t
connect by sdate + (level / 24) <= edate )
where to_char(hr, 'hh') = '07'
group by sdate, edate
UPDATE: As to #FlorinGhita's comment - fixed the query to include zero occurences
select sdate, edate, sum( decode(to_char(hr, 'hh'), '07',1,0))
from (select distinct edate, sdate, sdate + (level / 24) hr
from t
connect by sdate + (level / 24) <= edate )
group by sdate, edate

Answer 4

Do like this (in SQL)
declare #table table ( start datetime, ends datetime)
insert into #table select'2012-06-16 05:00','2012-06-16 08:00' --1
insert into #table select'2012-06-16 16:00','2012-06-16 20:00' --1
insert into #table select'2012-06-16 05:00','2012-06-16 07:00' --0
insert into #table select'2012-06-16 07:00','2012-06-16 19:00' --0
insert into #table select'2012-06-16 08:00','2012-06-16 15:00' --0
insert into #table select'2012-06-16 05:00','2012-06-16 19:01' --2
insert into #table select'2012-06-16 05:00','2012-06-18 20:00' --6
insert into #table select'2012-06-16 07:00','2012-06-18 07:00' --3
Declare #From DATETIME
Declare #To DATETIME
select #From = MIN(start) from #table
select #To = max(ends) from #table
;with CTE AS
(
SELECT distinct
DATEADD(DD,DATEDIFF(D,0,start),0)+'07:00' AS AimTime
FROM #table
),CTE1 AS
(
Select AimTime
FROM CTE
UNION ALL
Select DATEADD(hour, 12, AimTime)
From CTE1
WHERE AimTime< #To
)
select start,ends, count(AimTime)
from CTE1 right join #table t
on t.start < CTE1.AimTime and t.ends > CTE1.AimTime
group by start,ends