Question

Hard to put my question into a title. What I am looking for is a way to see which tasks were scheduled to run in the past 15 minutes.

I currently have a table that shows the window that a task should run and how often it should be kicked off within that window. However, I have no experience with this type of query. Hopefully somebody can help out a bit. I should also say that I’d like to do this without creating extra tables

Schedule Table

| taskID | startTime | endTime | everyMinutes |
|________|___________|_________|______________|
| 135467 |    8:00   |  20:00  |      15      |
| 675314 |    7:15   |  13:45  |      30      |

For example, in the above table, if the time was 9:18, the query would return both tasks

| taskID | scheduledTime|
|________|______________|
| 135467 |     9:15     |
| 675314 |     9:15     |

Where as if it was ran at 9:35 the query would only return 1 result

| taskID | scheduledTime|
|________|______________|
| 135467 |     9:30     |

Answer 1

You could use a numbers table to expand the Schedule table into a series of taskID, scheduledTime rows, then filter the rows to return only those that have scheduledTime within the last 15 minutes:

WITH expanded AS (
  SELECT
    s.taskID,
    scheduledTime = DATEADD(MINUTE, s.everyMinutes * n.N, s.startTime)
  FROM Schedule s
  INNER JOIN Numbers n
  ON n.N BETWEEN 0 AND DATEDIFF(MINUTE, s.startTime, s.endTime) / s.everyMinutes
)
SELECT e.*
FROM expanded e
CROSS APPLY (SELECT CAST(GETDATE() AS time)) x (now)
WHERE e.scheduledTime BETWEEN DATEADD(MINUTE, -15, x.now) AND x.now
;

You can try this query, as well as play with it, at SQL Fiddle.