CalcSwitchOnDuration

# VIEW: vswitcheventsdist - PASS 1 - retrieves only distinct on>off & off>on events
SELECT a.Id,
       a.FeedId,
       a.DateTime,
       a.Value
FROM
  (SELECT * ,
          LAG(Id) OVER (
                        ORDER BY datetime) AS prev
   FROM feedsdata
   WHERE feedid = 27
     AND (Value = 'on'
          OR Value = 'off')
   ORDER BY datetime) a
INNER JOIN feedsdata fd ON a.prev = fd.Id
WHERE a.Value <> fd.Value

####################################################3

# PASS 2 - calculate duration
SELECT dtStart,
       dtEnd,
       duration
FROM
  (SELECT a.datetime AS dtEnd,
          b.datetime AS dtStart,
          TIMESTAMPDIFF(MINUTE, b.datetime, a.datetime) AS duration
   FROM
     (SELECT * ,
             LAG(Id) OVER (
                           ORDER BY datetime) AS prev
      FROM vswitcheventsdist) a
   INNER JOIN vswitcheventsdist b ON a.prev = b.Id
   WHERE a.Value = 'off'
     AND b.Value = 'on' ) c

#######################

# Result

dtStart               | dtEnd                 | Duration
"2018-07-10 04:30:16"   "2018-07-10 04:54:12"   23
"2018-07-10 13:47:27"   "2018-07-10 14:34:48"   47
"2018-07-10 15:48:52"   "2018-07-10 15:49:08"   0
"2018-07-10 17:00:14"   "2018-07-10 17:14:15"   14