表結構：

資料：

需求：

  按照company_id不同分組，然後分別求出相同company_id相鄰記錄touch_time的差值

SQL:

  select r1.company_id,
       r1.touch_time,
       r2.touch_time,
       r1.touch_time - r2.touch_time
  from (select (@rownum := @rownum + 1) as rownum,
               info.company_id,
               info.touch_time
          from sys_touch_info info, (select @rownum := 0) r
         where info.touch_time is not null
         order by info.company_id) r1
  left join (select (@index := @index + 1) as rownum,
                    info.company_id,
                    info.touch_time
               from sys_touch_info info, (select @index := 0) r
              where info.touch_time is not null
              order by info.company_id) r2
    on r1.company_id = r2.company_id
   and r1.rownum = r2.rownum - 1

結果：