I have a set of call detail records, and from those records, I'm supposed to determine the average concurrent active calls per system, per hour (at a precision of one minute). If I query 7pm to 8pm, I should see the average concurrent calls for the hour (averaging the concurrent calls for each minute) within that hour (for each system).
So, I need a way to check for a count of active calls for 7:00-7:01, 7:01-7:02, etc then average those numbers. A call is considered active if the call's time and duration fall within the current minute being checked.
What makes this even more difficult is that it needs to span SQL 7.0 and SQL 2000 (some functions in 2000 aren't available in 7.0, such as GetUTCTime()), if I can just get 2000 working I'll be happy.
What approaches to this problem can I take?
I thought about looping through minutes (60) in the hour being checked and adding the count of calls that fall between that minute and then somehow cross referencing the duration to make sure that a call that starts at 7:00 pm and has a duration of 300 seconds shows active at 7:04, but I can't imagine how to approach the problem. I tried to figure out a way to weight each call against particular minute that would tell me if the call was active during that minute or not, but couldn't come up with an effective solution.
The data types here are the same as I have to query against. I don't have any control over the schema (other than possibly converting the data and inserting into another table with more appropriate data types). I've provided some example data that I know has concurrent active calls.
CREATE TABLE Records(
seconds char(10),
time char(4),
date char(8),
dur int,
system int,
port int,
)
--seconds is an stime value. It's the difference of seconds from UTC 1/1/1970 00:00:00 to the current UTC time, we use it as an identifier (like epoch).
--time is the time the call was made.
--date is the day the call was made.
--dur is the duration of the call in seconds.
--system is the system number.
--port is the port on the system (not particularly relevant for this question).
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924228','1923','20090416',105,2,2)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239923455','1910','20090416',884,1,97)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924221','1923','20090416',116,2,15)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924259','1924','20090416',90,1,102)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239923458','1910','20090416',891,2,1)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924255','1924','20090416',99,2,42)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924336','1925','20090416',20,2,58)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924293','1924','20090416',64,2,41)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239923472','1911','20090416',888,2,27)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924347','1925','20090416',25,1,100)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924301','1925','20090416',77,2,55)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924332','1925','20090416',52,2,43)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924240','1924','20090416',151,1,17)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924313','1925','20090416',96,2,62)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924094','1921','20090416',315,2,16)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239923643','1914','20090416',788,2,34)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924447','1927','20090416',6,2,27)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924342','1925','20090416',119,2,15)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924397','1926','20090416',76,2,41)
INSERT INTO Records(seconds, time, date, dur, system, port) VALUES('1239924457','1927','20090416',23,2,27)