Question

我有一个程序直接将我的MQTT消息保存到mySQL数据库中。我保存有效负载，主题和创建时间。我有不同的主题，遵循一定的顺序。

我有＆＃39;主题：开始，主题：带有效负载的阶段1：A，主题：带有效负载的阶段2：B和主题：停止＆＃39;。在此期间，我有大量的消息与恒定的温度数据馈送。

我看起来像这样：

| Topic          | Payload | Create_time           |
| 'start'        |         | '2016-05-17 10:00:00' |
| 'temperature'  | 5       | '2016-05-17 10:00:20' |
| 'temperature'  | 6       | '2016-05-17 10:01:20' |
| 'temperature'  | 6       | '2016-05-17 10:02:20' |
| 'temperature'  | 7       | '2016-05-17 10:03:20' |
| 'temperature'  | 8       | '2016-05-17 10:04:20' |
| 'phase1'       | 'A'     | '2016-05-17 10:04:30' |
| 'temperature'  | 8       | '2016-05-17 10:05:20' |
| 'temperature'  | 9       | '2016-05-17 10:06:20' |
| 'temperature'  | 10      | '2016-05-17 10:07:20' |
| 'phase2'       | 'B'     | '2016-05-17 10:08:30' |
| 'temperature'  | 10      | '2016-05-17 10:08:50' |
| 'stop'         |         | '2016-05-17 10:08:30' |
... more sequences like this where A and B are sequence specific

现在我想查询这些数据，使其成为这种格式：

 | Date         | Phase1 | Start sequence        | End sequence          | Phase2 |
 | '2016-05-17' | 'A'    | '2016-05-17 10:00:00' | '2016-05-17 10:08:30' | 'B'    |
 ...
 for every sequence where 
     - date is the date of that sequence (without time).
     - the var A of that sequence
     - the start create_time of that sequence
     - the end create_time of that sequence
     - the var B of that sequence.

如何将不同的行分组为序列，变量在开始和结束时间之间显示为有效负载？

Answer 1

您可以使用user defined variable标记序列（只要看到Topic='start'，就会递增）：

select date(min(Create_time)) `Date`, group_concat(if(Topic='phase1',Payload,null)) Phase1, 
  min(Create_time) `Start sequence`, 
  group_concat(if(Topic='stop',Create_time,null)) `End sequence`, 
  group_concat(if(Topic='phase2',Payload,null)) Phase2
from (
  select if(Topic='start',@id:=@id+1,@id) id, a.*
  from (
    select *
    from Table1
    order by Create_time) a
  join (select @id:=0) b) a
group by id;

sqlfiddle

查询在开始和结束行之间保存数据库中的mqtt消息

1 个答案: