mysql - sql - 如何对值进行分组？

Question

我有一张 table ，这样:

> SELECT * FROM tempLog WHERE DATE(ts) = CURDATE() LIMIT 9;

+-------+---------------------+----------+-------+-------+
| id    | ts                  | sensorid | value | event |
+-------+---------------------+----------+-------+-------+
| 11020 | 2017-12-15 00:00:01 |        3 |  18.1 | cron  |
| 11021 | 2017-12-15 00:00:01 |        4 |  14.8 | cron  |
| 11022 | 2017-12-15 00:00:01 |        5 |   1.3 | cron  |
| 11023 | 2017-12-15 00:02:02 |        3 |  18.1 | cron  |
| 11024 | 2017-12-15 00:02:02 |        4 |  14.8 | cron  |
| 11025 | 2017-12-15 00:02:02 |        5 |   1.3 | cron  |
+-------+---------------------+----------+-------+-------+

是否可以构造一个查询，以便我得到

+---------------------+---------+---------+---------+
| ts                  | sensor3 | sensor4 | sensor5 |
+---------------------+---------+---------+---------+
| 2017-12-15 00:00:01 |   18.1  |   14.8  |  1.3    |
| 2017-12-15 00:02:02 |   18.1  |   14.8  |  1.3    |
+---------------------+---------+---------+---------+

也就是说，选择所有不同的“时间戳”并从当时的不同传感器获取每个值。

传感器稍后会更多，所以我必须考虑到这一点。 他们都将在相同的“时间戳”进行轮询。

谢谢 /乔恩

Answer 1

select ts, 
       max(case when sensorid = 3 then value else 0 end) as sensor3,
       max(case when sensorid = 4 then value else 0 end) as sensor4,
       max(case when sensorid = 5 then value else 0 end) as sensor5
from your_table
group by ts