Mysql 如何每隔5秒选择和分组日期？

我在选择和分组时间方面遇到了问题 例如，我在数据库中获得以下时间：

2014-03-31 00:00:06
2014-03-31 00:00:06
2014-03-31 00:00:06
2014-03-31 00:00:16
2014-03-31 00:00:16
2014-03-31 00:00:16
2014-03-31 00:00:22
2014-03-31 00:00:22
2014-03-31 00:00:22
2014-03-31 00:00:26
2014-03-31 00:00:26
2014-03-31 00:00:26
2014-03-31 00:00:39
2014-03-31 00:00:39
2014-03-31 00:00:39
2014-03-31 00:00:42
2014-03-31 00:00:42
2014-03-31 00:00:42
2014-03-31 00:00:49
2014-03-31 00:00:49
2014-03-31 00:00:49
2014-03-31 00:00:58
2014-03-31 00:00:58
2014-03-31 00:00:58
2014-03-31 00:01:30
2014-03-31 00:01:30
2014-03-31 00:01:30
2014-03-31 00:01:39
2014-03-31 00:01:39
2014-03-31 00:01:39
2014-03-31 00:01:40
2014-03-31 00:01:40
2014-03-31 00:01:40
2014-03-31 00:01:47
2014-03-31 00:01:47
2014-03-31 00:01:47
2014-03-31 00:02:06
2014-03-31 00:02:06
2014-03-31 00:02:06
2014-03-31 00:02:09

我想以

5秒的间隔对它们进行分组并计数
例如

我尝试使用date_格式，但似乎无法按预期对它们进行分组

感谢所有SOER。
试试这个：

SELECT   sec_to_time(time_to_sec(col1)- time_to_sec(col1)%(5)) AS timekey, count(*)
FROM     mytable
GROUP BY timekey;

小提琴示例：

SELECT   sec_to_time(time_to_sec(col1)- time_to_sec(col1)%(5)) AS timekey, count(*)
FROM     mytable
GROUP BY timekey;

  select concat(date_format(dt,'%Y-%m-%d H:%i:'),lpad(floor(second(dt)/5)*5,2,'0')), count(*)
    from dates 
group by concat(date_format(dt,'%Y-%m-%d %H:%i:'),lpad(floor(second(dt)/5)*5,2,'0'));