SQL Query to get count of cycles if it matches value of column in consecutive rows

Question

I have table named vehicledata which consists 3 columns: id, Veh No, and Veh Mode.

My data looks like this:

Answer 1

One approach might be to approach this as a gaps and islands problem, and use the difference in row numbers method:

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY VehNo ORDER BY id) rn1,
        ROW_NUMBER() OVER (PARTITION BY VehNo, VehMode ORDER BY id) rn2
    FROM yourTable
)

SELECT VehNo, COUNT(DISTINCT rn1 - rn2) / 2 AS NumCycles
FROM cte
GROUP BY VehNo;

Demo

This assumes that every 2 islands corresponds to one driving cycle. A vehicle having IDLE/DRIVE/IDLE would therefore be counted as having only 1 cycle, since 3 / 2 truncates to 1 in integer division.