Access/SQL Interval breakout - sql

Question

EDIT: SIMPLIED CODE
CODE START END TLY
X 7/12/2016 10:30:00 AM 7/12/2016 11:00:00 AM 68
X 8/14/2016 09:30:00 AM 8/14/2016 11:00:00 AM 11
I was looking for some assistance with an odd table that I have pulled into Access (using SQL to query). The underlying issue I have is sometimes the data can be every 30 minutes as represented in line one (10:00-10:30) or it could be multiple intervals such as line two 09:30-11:00.
Ideally, I'd like to represent this as every 30 minute period they are reporting for so the data would look as follows:
CODE START END TLY
X 7/12/2016 10:30:00 AM 7/12/2016 11:00:00 AM 68
X 8/14/2016 09:30:00 AM 8/14/2016 10:00:00 AM 11
X 8/14/2016 10:00:00 AM 8/14/2016 10:30:00 AM 11
X 8/14/2016 10:30:00 AM 8/14/2016 11:00:00 AM 11
Code used:
SELECT
SGT.CODE AS CODE, CVDate((SGT.START_MOMENT-240)/1440) AS START,
CVDate((SGT.STOP_MOMENT-240)/1440) AS END,
SGT.TLY AS TLY
FROM
STF_GRP_TLY AS SGT
Any thoughts or suggestions that I could try?
Thank you!
George

Answer 1

Leaving aside your joins and date/time math [... - 240)/1440] for the moment, if you have a data table
[tblIntervals]
CODE START END TLY
------------ ------------------- ------------------- ---
Group_Sample 2016-07-12 10:30:00 2016-07-12 11:00:00 68
Group_Sample 2016-08-14 09:30:00 2016-08-14 11:00:00 11
and you create a "numbers table" that starts with zero and counts up (by one) to more than the maximum number of half-hour subintervals you would ever expect to encounter, e.g.
[tblNumbers]
n
--
0
1
2
3
4
5
6
7
8
9
then you can create a query that uses a cross-join to list the individual sub-intervals like so:
SELECT
tblIntervals.CODE,
DateAdd("n", 30 * tblNumbers.n, tblIntervals.START) AS dtmSTART,
DateAdd("n", 30 * (tblNumbers.n + 1), tblIntervals.START) AS dtmEND,
tblIntervals.TLY
FROM
tblIntervals, tblNumbers
WHERE
DateAdd("n", 30 * tblNumbers.n, tblIntervals.START) < tblIntervals.END
ORDER BY 1, 2
returning
CODE dtmSTART dtmEND TLY
------------ ------------------- ------------------- ---
Group_Sample 2016-07-12 10:30:00 2016-07-12 11:00:00 68
Group_Sample 2016-08-14 09:30:00 2016-08-14 10:00:00 11
Group_Sample 2016-08-14 10:00:00 2016-08-14 10:30:00 11
Group_Sample 2016-08-14 10:30:00 2016-08-14 11:00:00 11
Edit
To incorporate the conversion from "nominal" to "real" date/time values you could use a query like this:
SELECT
STF_GRP_TLY.STF_GRP_SK,
DateAdd("n", 30 * tblNumbers.n, CDate((STF_GRP_TLY.START_MOMENT-240)/1440)) AS dtmSTART,
DateAdd("n", 30 * (tblNumbers.n + 1), CDate((STF_GRP_TLY.START_MOMENT-240)/1440)) AS dtmEND,
STF_GRP_TLY.TLY
FROM STF_GRP_TLY, tblNumbers
WHERE
DateAdd("n", 30 * tblNumbers.n, CDate((STF_GRP_TLY.START_MOMENT-240)/1440)) < CDate((STF_GRP_TLY.STOP_MOMENT-240)/1440)
although I would be inclined to create a saved query that does the conversion to real date/time values ...
[qryIntervals]
SELECT
STF_GRP_SK,
CDate((START_MOMENT-240)/1440) AS START,
CDate((STOP_MOMENT-240)/1440) AS END,
TLY
FROM STF_GRP_TLY
... and then use it in the following simplified query to generate the sub-intervals
SELECT
qryIntervals.STF_GRP_SK,
DateAdd("n", 30 * tblNumbers.n, qryIntervals.START) AS dtmSTART,
DateAdd("n", 30 * (tblNumbers.n + 1), qryIntervals.START) AS dtmEND,
qryIntervals.TLY
FROM qryIntervals, tblNumbers
WHERE
DateAdd("n", 30 * tblNumbers.n, qryIntervals.START) < qryIntervals.END