mysql_存储过程_后一行减去前一行

DELIMITER $$
/*统计单个用户登录次数的存过
@times_count int  返回值 
@i 记录行号的变量  初始值为0
@temp 记录时间差的变量  
@total 记录登录次数的变量  初始值为0
@nums 记录共有多少行（单个用户）
@j 记录行号的变量 值为i+1
*/
CREATE PROCEDURE p_count_loginTimes(OUT times_count INT) 
BEGIN
  DECLARE i,
  temp,
  total,
  nums,
  j INT ;
  SET total = 0 ;
  SET i = 0 ;
  SELECT 
    COUNT(1) 
  FROM
    t_app_visit_detail INTO nums ;
  WHILE
    i <= nums DO SET j = i + 1 ;
    SELECT 
      TIMESTAMPDIFF(
        MINUTE,
        (SELECT 
          APP_END_TIME 
        FROM
          t_app_visit_detail 
        LIMIT i, 1),
        (SELECT 
          APP_START_TIME 
        FROM
          t_app_visit_detail 
        LIMIT j, 1)
      ) INTO temp ;
    IF temp > 30 
    THEN SET total = total + 1 ;
    END IF ;
    SET i = i + 1 ;
    SET times_count = total ;
  END WHILE ;
END $$
DELIMITER ;