SQL Server Active Record counts by month - sql

Question

I've created a database storing Incident tickets.
I have created a fact and a number of dimension tables.
Here is some sample data
+---------------------+--------------+--------------+-------------+------------+
| LastModifiedDateKey | TicketNumber | Status | factCurrent | Date |
+---------------------+--------------+--------------+-------------+------------+
| 2774 | T:9992260 | Open | 1 | 4/12/2017 |
| 2777 | T:9992805 | Open | 1 | 7/12/2017 |
| 2777 | T:9993068 | Open | 1 | 7/12/2017 |
| 2777 | T:9993098 | Open | 0 | 7/12/2017 |
| 2793 | T:9993098 | Acknowledged | 0 | 23/12/2017 |
| 2928 | T:9993098 | Closed | 1 | 5/01/2018 |
| 2777 | T:9993799 | Open | 0 | 7/12/2017 |
| 2928 | T:9993799 | Closed | 1 | 5/01/2018 |
| 2778 | T:9994729 | Open | 1 | 8/12/2017 |
| 2774 | T:9994791 | Open | 0 | 4/12/2017 |
| 2928 | T:9994791 | Closed | 1 | 5/01/2018 |
| 2777 | T:9994912 | Open | 1 | 7/12/2017 |
| 2778 | T:9995201 | Open | 0 | 8/12/2017 |
| 2793 | T:9995201 | Closed | 1 | 23/12/2017 |
| 2931 | T:9718629 | Open | 1 | 8/01/2018 |
| 2933 | T:9718629 | Closed | 1 | 10/01/2018 |
| 2932 | T:9855664 | Open | 1 | 9/01/2018 |
| 2931 | T:9891975 | Open | 1 | 8/01/2018 |
+---------------------+--------------+--------------+-------------+------------+
I want a query that will give me the total of tickets open at the end of each month.
In the data January should have 8 and Feb 2.
Note: that a ticket can have multiple rows with same status because a dimension key has changed or multiple rows with different status all in the same month. e.g. T:9993098.

Answer 1

This approach first uses ROW_NUMBER to identify the most recent record for each ticket, for each month/year. It is assumed that the most recent record in a month will contain the status in which a ticket ended for that month. Then, it aggregates over this modified table, counting only tickets which ended the month in an open status.
SELECT
YEAR(Date) + "-" + MONTH(Date) AS date,
COUNT(*) AS num_open_tickets
FROM
(
SELECT *,
ROW_NUMBER() OVER (PARITION BY YEAR(Date), MONTH(Date), TicketNumber
ORDER BY BY Date DESC) rn
FROM yourTable
) t
WHERE t.rn = 1 AND t.Status = 'Open'
GROUP BY
YEAR(Date) + "-" + MONTH(Date);

Answer 2

First, I would generate the months. Then do a cumulative count of the opens minus the closes. Alas, that is a bit tricky because of the repeated rows for a ticket and because you are using an old version of SQL Server.
But . . . you can do this:
with months as (
select dateadd(day, 1 - day(min(date)), min(date)) as mon_start,
max(date) as max_date
from sample
union all
select dateadd(month, 1, mon_start), max_date
from months
where dateadd(month, 1, mon_start) < max_date
)
select m.mon_end,
(select count(distinct case when status = 'Open' then ticket end) -
count(distinct case when status = 'Closed' then ticket end)
from sample s
where s.date <= m.mon_end
) as open_tickets
from (select dateadd(day, -1, mon_start) as mon_end
from months
) m;
This uses a recursive CTE to generate the months. It is easier to generate the first day of the months and then subtract one day afterwards (what is the date when you add 1 month to the last day of February?)
The rest uses a correlated subquery to count the number of open tickets on that date.