Detect Anomaly Intervals with SQL

Question

My problem is simple: I have a table with a series of statuses and timestamps (for the sake of curiosity, these statuses indicate alarm levels) and I would like to query this ta

Answer 1

Finally figured out a version I was happy with. It took me remembering an answer from another question (can't remember which one though) where it was pointed out that the difference between two (increasing) sequences was always a constant.

WITH Ordered (occurredAt, status, row, grp) 
             as (SELECT occurredAt, status, 
                        ROW_NUMBER() OVER (ORDER BY occurredat), 
                        ROW_NUMBER() OVER (PARTITION BY status 
                                           ORDER BY occurredat)
                 FROM Alert)

SELECT Event.startDate, Ending.occurredAt as endDate,
       DATEDIFF(second, Event.startDate, Ending.occurredAt) as interval

FROM (SELECT MIN(occurredAt) as startDate, MAX(row) as ending
      FROM Ordered
      WHERE status = 2
      GROUP BY row - grp) Event

LEFT JOIN (SELECT occurredAt, row
           FROM Ordered
           WHERE status != 2) Ending
        ON Event.ending + 1 = Ending.row

(working SQL Fiddle example, with some additional data rows for work checking).

This unfortunately doesn't correctly deal with level-2 statuses that are end rows (behavior unspecified), although it does list them.