How to optimize iterative approach into set based approach

Question

I have an iterative query that I need to optimize with hopefully a set based approach. Every hour it looks at a vehicles gps data and loops over the
data points looking for idle times longer than X minutes. If the vehicle has been idle, but less than X minutes and it starts moving, the idle time is reset, and begins checking for the threshold again when the speed <= 1.
For each vehicle, I only want to know the consecutive idle times greater than X seconds. the thing to note as well, if the idle time doesn't reach the threshold and
the vehicle starts moving, the time is then considered moving time and not idle time.
here is the query - Thanks in advance for any help!
WHILE @iLoop = 1
BEGIN
If( @iCurRow is null) select @iCurRow = 1
Else select @iCurRow = @iCurRow + 1
IF @iCurRow is null Break
select @curTS = TS,
@curIgn = IgnitionOn,
@curSpeed = Speed,
@span = 0
from @temp where ID = @iCurRow
select @nextTS = TS,
@nextSpeed = Speed
from @temp where ID = @iCurRow+1
set @span= isnull(sum(datediff(second,@curTS, @nextTS)),0)
if(@curSpeed <= 1 and @curIgn = 1)
Begin
if(@isIdling = 1)
Begin
set @adjIdle = @adjIdle + @span
End
else if((@cumIdle + @span) >= @idleThreshold)
Begin
set @adjIdle = @adjIdle + @cumIdle + @span
set @cumIdle = 0
set @isIdling = 1
End
else
Begin
set @isIdling = 0
set @cumIdle = @cumIdle + @span
End
End
else if(@curSpeed > 1 and @curIgn = 1)
Begin
set @isIdling = 0
set @adjMove = @adjMove + @cumIdle + @span
set @cumIdle = 0
End
else if @curIgn = 1
Begin
set @isIdling = 0
set @cumIdle = @cumIdle + @span
End
else if @curIgn = 0
Begin
if((@cumIdle) >= @idleThreshold)
Begin
set @adjIdle = @adjIdle + @cumIdle
set @cumIdle = 0
set @isIdling = 0
End
else
Begin
set @adjMove = @adjMove + @cumIdle
set @cumIdle = 0
set @isIdling = 0
End
End
IF @iCurRow+1 = @iMaxRow Break;
END
End

Answer 1

I molded your sample data into INSERT statements (please provide the INSERT
statements yourself next time), and declare variables. I defined the
threshold, and I added a SELECT of what I think is the final output. But it
returns 0 and not 10 as suggested. I have probably not understood the
problem correctly.
Whether this can be done set-based for a single vehicle, I don't know, but I
assume that you are looking at many vehicles at a time. What you definitely
can do is to work with all vehicles at the same time. Number the rows per
vehicle, and the work with all rowno = 1 at once, then rowno = 2 at once
etc.
This is my script as far as I got.
declare @temp as table
   ID int identity,
   TS datetime2,
   IgnitionOn bit,
   Speed decimal(4,1),
   GPIO1 bit,
   GPIO2 bit,
   Location varchar(3),
   Odometer bigint,
   Lat decimal (9,6),
   Lng decimal (9,6)
INSERT @temp (TS, Speed, IgnitionOn)
VALUES
('12:00',   5,   1)   ,
('12:02',   0,   1)   ,
('12:04',   0.5,   1),
('12:06',   0,   1)   ,
('12:08',   0.25,   1),
('12:10',   0,   1)   ,
('12:12',   2,   1)   ,
('12:14',   6,   1)   ,
('12:16',   10,   1) ,
('12:18',   0,   1)    ,
('12:20',   0,   1)   ,
('12:22',   15,   1),
('12:24',   20,   1),
('12:26',   30,   1),
('12:28',   0,   1),
('12:30',   0,   1)
DECLARE @iLoop int = 1,
        @iCurRow int,
        @curTS datetime2,
        @curIgn bit,
        @curSpeed decimal(4, 1),
        @nextTS datetime2 ,
        @nextSpeed decimal(4,1),
        @span      int,
        @isIdling  bit,
        @adjIdle   int,
        @cumIdle       int,
        @idleThreshold int = 10,
        @cumIdling     int,
        @adjMove       int,
        @iMaxRow       int  = (SELECT MAX(ID) FROM @temp)
WHILE @iLoop = 1
BEGIN
          If( @iCurRow is null) select @iCurRow = 1
          Else select @iCurRow = @iCurRow + 1
          IF @iCurRow is null Break
          select @curTS = TS,
                 @curIgn = IgnitionOn,
                 @curSpeed = Speed,
                 @span = 0
               from @temp where  ID = @iCurRow
          select @nextTS = TS,
                  @nextSpeed = Speed
               from @temp where  ID = @iCurRow+1
          set @span= isnull(sum(datediff(second,@curTS, @nextTS)),0)
          if(@curSpeed <= 1 and @curIgn = 1)
          Begin
               if(@isIdling = 1)
               Begin
                    set @adjIdle = @adjIdle + @span
               End
               else if((@cumIdle + @span) >= @idleThreshold)
               Begin
                    set @adjIdle = @adjIdle + @cumIdle + @span
                    set @cumIdle = 0
                    set @isIdling = 1
               End
               else
               Begin
                    set @isIdling = 0
                    set @cumIdle = @cumIdle + @span
               End
          End
          else if(@curSpeed > 1 and @curIgn = 1)
          Begin
               set @isIdling = 0
               set @adjMove = @adjMove + @cumIdle + @span
              set @cumIdle = 0
          End         
          else if @curIgn = 1
          Begin
               set @isIdling = 0
               set @cumIdle = @cumIdle + @span
          End
          else if @curIgn = 0
          Begin
               if((@cumIdle) >= @idleThreshold)
               Begin
                    set @adjIdle = @adjIdle + @cumIdle
                    set @cumIdle = 0
                    set @isIdling = 0
               End
               else
               Begin
                    set @adjMove = @adjMove + @cumIdle
                    set @cumIdle = 0
                    set @isIdling = 0
               End
          End
          IF @iCurRow+1 = @iMaxRow Break;
     END
--End
SELECT @cumIdle
Erland Sommarskog, SQL Server MVP, [email protected]