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

@Pradeep - The logic to build this query will be to check only rows where vehicle is currently in drive mode and he was IDLE before that ROW. You don't have to worry about IDLE modes and also the continuous DRIVE modes. You only need to check the rows where a vehicle has transitioned from IDLE to DRIVE. I have used a case statement and a LAG windows function to mark only these records as 1 and everything else as 0. And then I just took a sum of this column for each vehicle.

------------------------
WITH vehicles(id , Veh_No,  Veh_Mode) AS
( 
SELECT 1 ,  'KA03-003',   'IDLE'  UNION
SELECT 2 ,  'KA03-003',   'IDLE'  UNION
SELECT 3 ,  'KA03-003',   'IDLE'  UNION
SELECT 4 ,  'KA03-003',   'DRIVE' UNION
SELECT 5 ,  'KA03-003',   'DRIVE' UNION
SELECT 6 ,  'KA03-003',   'DRIVE' UNION
SELECT 7 ,  'KA03-003',   'DRIVE' UNION
SELECT 8 ,  'KA03-003',   'DRIVE' UNION
SELECT 9 ,  'KA03-003',   'IDLE'  UNION
SELECT 10,  'KA03-003',   'IDLE'  UNION
SELECT 11,  'KA03-003',   'IDLE'  UNION
SELECT 12,  'KA03-003',   'DRIVE' UNION
SELECT 13,  'KA03-003',   'DRIVE' UNION
SELECT 14,  'KA03-003',   'DRIVE' UNION
SELECT 15,  'KA03-003',   'DRIVE' UNION
SELECT 16,  'KA05-005',   'IDLE'  UNION
SELECT 17,  'KA05-005',   'IDLE'  UNION
SELECT 18,  'KA05-005',   'IDLE'  UNION
SELECT 19,  'KA05-005',   'DRIVE' UNION
SELECT 20,  'KA05-005',   'DRIVE' UNION
SELECT 21,  'KA05-005',   'DRIVE' UNION
SELECT 22,  'KA05-005',   'DRIVE' UNION
SELECT 23,  'KA05-005',   'DRIVE' UNION
SELECT 24,  'KA05-005',   'IDLE'  UNION
SELECT 25,  'KA05-005',   'IDLE'  UNION
SELECT 26,  'KA05-005',   'IDLE'  UNION
SELECT 27,  'KA05-005',   'DRIVE' UNION
SELECT 28,  'KA05-005',   'DRIVE' UNION
SELECT 29,  'KA05-005',   'DRIVE' UNION
SELECT 30,  'KA05-005',   'DRIVE'
)

SELECT veh_no, SUM(count_drive_cycle) AS drive_cycles
FROM (SELECT *,
      CASE WHEN Veh_Mode = 'DRIVE'
            AND LAG(veh_mode,1,'DRIVE') OVER (PARTITION BY Veh_No ORDER BY id) = 'IDLE'   -- check if prev mode is IDLE
           THEN 1
           ELSE 0 END AS count_drive_cycle
      FROM vehicles
     ) A
GROUP BY veh_no

Answer 2

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).

Answer 3

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.