How to make a sql loop query to check difference b

Question

first of all, I'm not a native english speaker and this is a hard to explain issue. If you have any doubts, please let me know.

We're using a GPS vehicle tracking device, which is programmed to send and store in a DB the position of the vehicle every 5 min when not moving, and every 100 meters when moving.

This DB has a table called "vehicle_gps" that stores the data, with values such as speed, position, datetime, vehicle_gps_id.

I need some kind of query that will show the different positions where the vehicle stopped for more than a certain amount of time(e.g 2 minutes, discarding traffic lights).

For instance, I need something that can tell me the following: "The vehicle was on Positon1 (P1) at 8:00, it left P1 towards P2, reaching it at 8.20. The vehicle stayed at P2 until 10.20 and it reached P3 at 10.50"

example of the records in the table

vehicle_gps_id  | datetime---------- | latitude | longitude | speed

1000------------| 05/16/2012 08:00:00|50.0000   |50.00000   |40 (km/h)
1001------------| 05/16/2012 08:01:00|51.0000   |51.00000   |38 (km/h)
1002------------| 05/16/2012 08:01:23|51.0045   |50.000054  |40 (km/h)
1003------------| 05/16/2012 08:01:40|51.00540  |51.0005430 |39 (km/h)
.
.
.
1040------------| 05/16/2012 08:20:40|53.00540  |53.0005430 |0 (km/h)
1041------------| 05/16/2012 08:25:40|53.00540  |53.0005430 |0 (km/h)
1042------------| 05/16/2012 08:30:40|53.00540  |53.0005430 |0 (km/h)
.
.
.
1060------------| 05/16/2012 10:20:40|53.00540|53.0005430|20 (km/h)

How can I do something like that?

So far, I was able to get the difference in minutes between fixed positions and for that reason, I wanted a loop that would check all dates between positions and break whenever that difference was longer than 5 minutes, which means that the vehicle had stopped.

TIA

Answer 1

DECLARE @idFrom as int,
        @idTo as int,
        @gpsDateFrom as datetime,
        @gpsDateTo as datetime
DECLARE VehicleCursor CURSOR FAST_FORWARD FOR 
SELECT  vehicle_gps_id, 
        datetimeCol
FROM    yourtable
ORDER BY vehicle_gps_id
OPEN VehicleCursor FETCH NEXT FROM VehicleCursor INTO @idFrom, @gpsDateFrom
    FETCH NEXT FROM VehicleCursor INTO @idTo, @gpsDateTo
    WHILE @@FETCH_STATUS = 0 BEGIN 
        IF DATEDIFF(MI,@gpsDateFrom,@gpsDateTo) >5
        BEGIN
            --Break (your code here)
        END
        SET @idFrom = @idTo
        SET @gpsDateFrom = @gpsDateTo
        FETCH NEXT FROM VehicleCursor INTO @idTo, @gpsDateTo
    END 
CLOSE VehicleCursor 
DEALLOCATE VehicleCursor

Something like this should work for you. It is a cursor that just runs through all your columns comparing datetimes. You can enter in whatever you want to do into the commented section after the if statement.