试试这个：
表架构：

CREATE TABLE A(id INT, session_id INT,Event VARCHAR(20), created DATETIME);

INSERT INTO A VALUES(1, 101,'Start','2010/10/01 9:30:10')
,(2, 102,'Start'  , '2010/10/01 9:31:10')
,(3, 101,'End'    , '2010/10/01 9:32:10')
,(4, 103,'Start'  , '2010/10/01 9:35:10')
,(5, 102,'End'    , '2010/10/01 9:38:10')
,(6, 103,'End'    , '2010/10/01 9:39:10')
,(7, 101,'Start'  , '2010/10/01 9:39:10')
,(8, 102,'Start'  , '2010/10/01 9:39:10')
,(9, 101,'End'    , '2010/10/01 9:55:10');

查询：

SELECT D.session_id
    ,TIMESTAMPDIFF(MINUTE,MIN(D.created), MAX(D.created)) time_count
FROM(
  SELECT a.id,a.session_id,a.created
    ,ROUND(count(*)/2,0) as RN 
    ,count(*) as row_number1 
  FROM a AS a
  JOIN a AS b ON a.session_id = b.session_id AND a.id >= b.id
  GROUP BY a.id,a.session_id,a.created
  ORDER BY 2,3
    )D
GROUP BY D.session_id,D.RN
HAVING COUNT(1)>1

输出：

session_id  time_count
101         2
102         7
103         4
101         16

小提琴：
检查#sql fiddle中的输出

你可以试试它的辛塔克斯：

WITH cte AS (
    SELECT
        session_id,
        DATEDIFF(minute, created, LAG(created, 1)) AS diff,
        ROW_NUMBER() OVER (PARTITION BY session_id ORDER BY created) rn
    FROM yourTable
)

SELECT

        session_id,
        diff AS time_count
    FROM cte
    WHERE rn % 2 = 0

;

SELECT session_id,
DATEDIFF(MINUTE, MAX(created), MIN(created)) AS diff
FROM table
GROUP BY session_id