MySQL查找两个日期不同列之间的差异

这是我的疑问：

    select calldate as call_start, DATE_ADD(calldate, Interval duration SECOND) as call_end, duration
    from extensions 
    where ext = '2602' -- ext is the primary key
    AND DATE_FORMAT(calldate, '%Y-%m-%d') = "2015-03-20"
    order by calldate asc

返回以下内容：

如何添加第四列以获得第二行的call_start与第一行的call_end之间的差异？大概是这样的：

2015-03-20 10:21:20-2015-03-20 10:21:16=>4秒，这4秒应添加为第二行的第四个字段

因此，对于所有呼叫，它应该是这样的：

call_start           call_end              duration       difference
2015-03-20 10:19:41  2015-03-20 10:21:16   95             null
2015-03-20 10:21:20  2015-03-20 10:21:29   9              4

因为第一行没有前面调用的call\u end，所以应该有null

解决方案：

 SET @prev_end=null;
 select calldate, date_add(calldate, interval duration SECOND) as end_date, duration,
  TIME_FORMAT(SEC_TO_TIME(timestampdiff(second,@prev_end,calldate)), '%i:%s')as difference,
  @prev_end:= date_add(calldate, interval duration SECOND) as test
  from extensions
  where ext = '2602'
  AND DATE_FORMAT(calldate, '%Y-%m-%d') = "2015-03-20"
  order by calldate asc;

输出：

---

考虑下表

mysql> select * from extensions;
+---------------------+----------+
| calldate            | duration |
+---------------------+----------+
| 2015-03-20 10:19:41 |       95 |
| 2015-03-20 10:21:20 |        9 |
| 2015-03-20 10:21:35 |      277 |
| 2015-03-20 10:55:49 |       27 |
+---------------------+----------+

现在，您可以得到如下差异：

select
calldate as start_date,
end_date,
duration,
difference
from(
  select 
  calldate, 
  duration,
  date_add(calldate, interval duration SECOND) as end_date , 
  timestampdiff(second,@prev_end,calldate) as difference,
  @prev_end:= date_add(calldate, interval duration SECOND)
  from extensions,(select @prev_end:=null)x 
  order by calldate
)x

+---------------------+---------------------+----------+------------+
| start_date          | end_date            | duration | difference |
+---------------------+---------------------+----------+------------+
| 2015-03-20 10:19:41 | 2015-03-20 10:21:16 |       95 |       NULL |
| 2015-03-20 10:21:20 | 2015-03-20 10:21:29 |        9 |          4 |
| 2015-03-20 10:21:35 | 2015-03-20 10:26:12 |      277 |          6 |
| 2015-03-20 10:55:49 | 2015-03-20 10:56:16 |       27 |       1777 |
+---------------------+---------------------+----------+------------+

在上面的查询中，您需要在子查询中的where子句之前添加额外的where子句

where ext = '2602' -- ext is the primary key
AND DATE_FORMAT(calldate, '%Y-%m-%d') = "2015-03-20"

---

您可以使用MySQL用户定义的变量。 以下是有助于您的查询：

SET @end=null; -- reset the variable
SELECT 
      calldate as call_start,  
      DATE_ADD(calldate, Interval duration SECOND) as call_end, 
      TIMESTAMPDIFF(SECOND, call_start, @end) as prev_diff, 
      @end:=DATE_ADD(calldate, Interval duration SECOND)
FROM extensions 
WHERE ext = '2602' -- ext is the primary key
AND DATE_FORMAT(calldate, '%Y-%m-%d') = "2015-03-20"
ORDER BY calldate asc

---

将两个日期都转换为unix时间戳格式，然后您就可以找到差异。@Nodedy问题不是转换，问题是我找不到查询的逻辑。您能告诉我差异列的含义吗？@Nodedy获取call_从第二行开始与call_从第一行结束之间的差异，依此类推。。