MySQL查询获取温度趋势 [英] Mysql query to get trend of temperature
问题描述
我有一张很大的桌子,每1分钟记录一次温度,我想查询的是一个趋势;诸如每个选定时间段(一个小时或15分钟;取决于查询)的百分比增加或百分比减少
I have a very large table where I have temperatures getting logged every 1 mins, what I would like to query is a trend; something like a percentage increase or percentage decrease per selected period ( hour or 15mins; depending on the query)
我的表看起来(示例)如下
my table looks (example) like the following
ID time temp
119950 2013-03-27 07:56:05 27.25
119951 2013-03-27 07:57:05 27.50
119952 2013-03-27 07:58:05 27.60
119953 2013-03-27 07:59:05 27.80
119954 2013-03-27 08:00:05 27.70
119955 2013-03-27 08:01:05 27.50
119956 2013-03-27 08:02:05 27.25
119957 2013-03-27 08:03:05 27.10
119958 2013-03-27 08:04:05 26.9
119959 2013-03-27 08:05:05 27.1
119960 2013-03-27 08:06:05 27.25
119961 2013-03-27 08:07:05 27.6
我认为可以按如下方式计算趋势(按照链接),但是如果您有更好的方法,请指正; 取每行之间的差,然后相加然后除以计数.因此,对于上表,我们得到
I believe a trend can be calculated as follow (as per link), but correct me if you have a better way; take the difference between each row then add then up and divide by count. so for the table above we get
Diff
+0.25
+0.10
+0.20
-0.10
-0.20
-0.25
-0.15
-0.20
+0.20
+0.15
+0.35
最近11分钟的每分钟趋势是diff/11的总和.在过去的11分钟内,每分钟给出0.063C.
The trend per minute for last 11 minutes is sum of diff/11. which gives 0.063C per minute for last 11minutes.
有人可以帮我获取最近3小时每小时的百分比趋势吗?和每分钟1小时的趋势?
Can someone please help me get percentage trend per hour for last 3 hours. and trend per minute for 1 hour?
推荐答案
CREATE TABLE temperature_log
(ID INT NOT NULL,dt DATETIME NOT NULL, temperature DECIMAL(5,2) NOT NULL);
INSERT INTO temperature_log VALUES
(119950 ,'2013-03-27 07:56:05',27.25),
(119951 ,'2013-03-27 07:57:05', 27.50),
(119952 ,'2013-03-27 07:58:05', 27.60),
(119953 ,'2013-03-27 07:59:05', 27.80),
(119954 ,'2013-03-27 08:00:05', 27.70),
(119955 ,'2013-03-27 08:01:05', 27.50),
(119956 ,'2013-03-27 08:02:05', 27.25),
(119957 ,'2013-03-27 08:03:05', 27.10),
(119958 ,'2013-03-27 08:04:05', 26.9),
(119959 ,'2013-03-27 08:05:05', 27.1),
(119960 ,'2013-03-27 08:06:05', 27.25),
(119961 ,'2013-03-27 08:07:05', 27.6);
SELECT x.*
, x.temperature - y.temperature diff
, COUNT(*) cnt
,(x.temperature-y.temperature)/COUNT(*) trend
FROM temperature_log x
JOIN temperature_log y
ON y.id < x.id
GROUP
BY x.id;
+--------+---------------------+-------------+-------+-----+-----------+
| ID | dt | temperature | diff | cnt | trend |
+--------+---------------------+-------------+-------+-----+-----------+
| 119951 | 2013-03-27 07:57:05 | 27.50 | 0.25 | 1 | 0.250000 |
| 119952 | 2013-03-27 07:58:05 | 27.60 | 0.35 | 2 | 0.175000 |
| 119953 | 2013-03-27 07:59:05 | 27.80 | 0.55 | 3 | 0.183333 |
| 119954 | 2013-03-27 08:00:05 | 27.70 | 0.45 | 4 | 0.112500 |
| 119955 | 2013-03-27 08:01:05 | 27.50 | 0.25 | 5 | 0.050000 |
| 119956 | 2013-03-27 08:02:05 | 27.25 | 0.00 | 6 | 0.000000 |
| 119957 | 2013-03-27 08:03:05 | 27.10 | -0.15 | 7 | -0.021429 |
| 119958 | 2013-03-27 08:04:05 | 26.90 | -0.35 | 8 | -0.043750 |
| 119959 | 2013-03-27 08:05:05 | 27.10 | -0.15 | 9 | -0.016667 |
| 119960 | 2013-03-27 08:06:05 | 27.25 | 0.00 | 10 | 0.000000 |
| 119961 | 2013-03-27 08:07:05 | 27.60 | 0.35 | 11 | 0.031818 |
+--------+---------------------+-------------+-------+-----+-----------+
顺便说一句,如果您有兴趣每小时获取平均结果,则可以执行以下操作...
Incidentally, if you're interested in getting average results per hour, you could do something like this...
SELECT DATE_FORMAT(x.dt,'%Y-%m-%d %h:00:00')
, AVG(x.temperature) avg_temp
FROM temperature_log x
GROUP
BY DATE_FORMAT(x.dt,'%Y-%m-%d %h:00:00');
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