基于条件计算事件的总时间

CREATE TABLE log (  
     id INT NOT NULL AUTO_INCREMENT,  
     dt DATETIME NOT NULL,
     status VARCHAR(255),  
     PRIMARY KEY  (id)  
);

INSERT INTO log VALUES
(1, '2018-07-10 12:01:00' ,'keyout'),
(2, '2018-07-10 12:02:00' ,'keyout'),
(3, '2018-07-10 12:03:00' ,'keyinside'),
(4, '2018-07-10 12:44:00' ,'keyout'),
(5, '2018-07-10 13:02:00' ,'keyinside');


SELECT MIN(dt) dto 
     , dti
     , SEC_TO_TIME(TIME_TO_SEC(dti)-TIME_TO_SEC(MIN(dt))) diff
  FROM 
     (  SELECT x.dt
             , MIN(y.dt) dti
          FROM log x
          JOIN log y ON y.dt > x.dt 
           AND y.status = 'keyinside'
         WHERE x.status = 'keyout'
         GROUP 
            BY x.dt
     ) a
 GROUP
    BY dti;

    +---------------------+---------------------+----------+
    | dto                 | dti                 | diff     |
    +---------------------+---------------------+----------+
    | 2018-07-10 12:01:00 | 2018-07-10 12:03:00 | 00:02:00 |
    | 2018-07-10 12:44:00 | 2018-07-10 13:02:00 | 00:18:00 |
    +---------------------+---------------------+----------+