SQL Server 2022

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CREATE TABLe Activity  (machine_id int ,
process_id 	int,
activity_type 	VARCHAR(10) NOT NULL CHECK (activity_type IN('begin', 'end')),
timestamp 	float)
INSERT INTO Activity  VALUES(1,1,'Begin', 1.2),(1,1,'End', 2.2),(1,2,'Begin', 3.2),(1,2,'End', 5.2)
4 rows affected

WITH CTE AS (SELECT a1.machine_id, process_id 
 , 
 CASE WHEN  activity_type = 'end' Then a1.timestamp 
  -  LAG(a1.timestamp) OVER (PARTITION BY machine_id,process_id ORDER BY activity_type ) END
   processing_time
FROM Activity AS a1)
  SELECT machine_id,
  ROUND(AVG(processing_time),3) as processing_time 
  FROM CTE
WHERE processing_time IS NOT NULL
  GROUP BY machine_id


machine_id
processing_time


1
1.5


select a1.machine_id, round(avg(a2.timestamp-a1.timestamp), 3) as processing_time 
from Activity a1
join Activity a2 
on a1.machine_id=a2.machine_id and a1.process_id=a2.process_id
and a1.activity_type='start' and a2.activity_type='end'
group by a1.machine_id


machine_id
processing_time