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

You can just count the number of rows that have 'DRIVE' where the previous row has a different mode or NULL. For that, uselag()`:

select veh_no, count(*)
from (select t.*,
             lag(veh_mode) over (partition by veh_no order by id) as prev_veh_mode
      from t
     ) t
where veh_mode = 'DRIVE' and
      (prev_veh_mode <> 'DRIVE' or prev_veh_mode is null)
group by veh_no;

Here is a db<>fiddle (which happens to use MySQL but the code should work in any database).