所以,我在尝试计算 MySQL 查询中的平均值时有点卡住了。我要做的是从两张表中读取数据,其中一张很小,并且有描述房间、序列号、海拔和其他传感器数据的条目。另一个表包含每个序列号的温度输出记录。这是每个表的一些示例数据。
+------------------+-------+------+-----------+---------+--------+-----------+
| serial | room | rack | elevation | type | system | threshold |
+------------------+-------+------+-----------+---------+--------+-----------+
| 2D0008017075F210 | 2B211 | 5 | 5 | DS18S20 | test | 68 |
| 1D00080170496D10 | 2B211 | 5 | 5 | DS18S20 | test | 68 |
| 380008017037ED10 | 2B211 | 5 | 5 | DS18S20 | test | 68 |
+------------------+-------+------+-----------+---------+--------+-----------+
+------------------+---------------------+---------+
| serial | dtg | reading |
+------------------+---------------------+---------+
| 2D0008017075F210 | 2013-08-02 12:30:28 | 98.6 |
| 1D00080170496D10 | 2013-08-02 12:30:28 | 73.4 |
| 380008017037ED10 | 2013-08-02 12:30:28 | 79.7 |
| 2D0008017075F210 | 2013-08-02 12:30:38 | 98.6 |
| 1D00080170496D10 | 2013-08-02 12:30:38 | 73.4 |
| 380008017037ED10 | 2013-08-02 12:30:38 | 79.7 |
| 2D0008017075F210 | 2013-08-02 12:30:48 | 98.6 |
| 1D00080170496D10 | 2013-08-02 12:30:48 | 73.4 |
| 380008017037ED10 | 2013-08-02 12:30:48 | 79.7 |
| 2D0008017075F210 | 2013-08-02 12:30:58 | 98.6 |
| 1D00080170496D10 | 2013-08-02 12:30:58 | 73.4 |
| 380008017037ED10 | 2013-08-02 12:30:58 | 79.7 |
| 2D0008017075F210 | 2013-08-02 12:31:08 | 98.6 |
| 1D00080170496D10 | 2013-08-02 12:31:08 | 73.4 |
| 380008017037ED10 | 2013-08-02 12:31:08 | 79.7 |
| 2D0008017075F210 | 2013-08-02 12:31:18 | 98.6 |
| 1D00080170496D10 | 2013-08-02 12:31:18 | 73.4 |
| 380008017037ED10 | 2013-08-02 12:31:18 | 79.7 |
+------------------+---------------------+---------+
我有一个 SQL 查询,它可以将数据格式化为一个表格,然后我将其转换为 JSON 并传递给 Web 浏览器进行可视化。它看起来与此类似,虽然有点不同,因为我使用存储过程来修改时间间隔。
SELECT sensor_data.serial, sensor_data.dtg, sensor_data.reading, sensor.elevation,sensor.room, sensor.system FROM sensor_data, sensor WHERE sensor.serial = sensor_data.serial AND sensor_data.dtg BETWEEN NOW() - INTERVAL 1 MINUTE AND NOW();
结果看起来像这样
+------------------+---------------------+---------+-----------+-------+--------+
| serial | dtg | reading | elevation | room | system |
+------------------+---------------------+---------+-----------+-------+--------+
| 2D0008017075F210 | 2013-08-02 12:34:39 | 98.6 | 5 | 2B211 | test |
| 2D0008017075F210 | 2013-08-02 12:34:49 | 98.6 | 5 | 2B211 | test |
| 2D0008017075F210 | 2013-08-02 12:34:59 | 98.6 | 5 | 2B211 | test |
| 2D0008017075F210 | 2013-08-02 12:35:09 | 98.6 | 5 | 2B211 | test |
| 2D0008017075F210 | 2013-08-02 12:35:19 | 98.6 | 5 | 2B211 | test |
| 2D0008017075F210 | 2013-08-02 12:35:29 | 98.6 | 5 | 2B211 | test |
| 1D00080170496D10 | 2013-08-02 12:34:39 | 73.4 | 5 | 2B211 | test |
| 1D00080170496D10 | 2013-08-02 12:34:49 | 73.4 | 5 | 2B211 | test |
| 1D00080170496D10 | 2013-08-02 12:34:59 | 73.4 | 5 | 2B211 | test |
| 1D00080170496D10 | 2013-08-02 12:35:09 | 73.4 | 5 | 2B211 | test |
| 1D00080170496D10 | 2013-08-02 12:35:19 | 73.4 | 5 | 2B211 | test |
| 1D00080170496D10 | 2013-08-02 12:35:29 | 73.4 | 5 | 2B211 | test |
| 380008017037ED10 | 2013-08-02 12:34:39 | 79.7 | 5 | 2B211 | test |
| 380008017037ED10 | 2013-08-02 12:34:49 | 79.7 | 5 | 2B211 | test |
| 380008017037ED10 | 2013-08-02 12:34:59 | 79.7 | 5 | 2B211 | test |
| 380008017037ED10 | 2013-08-02 12:35:09 | 79.7 | 5 | 2B211 | test |
| 380008017037ED10 | 2013-08-02 12:35:19 | 79.7 | 5 | 2B211 | test |
| 380008017037ED10 | 2013-08-02 12:35:29 | 79.7 | 5 | 2B211 | test |
+------------------+---------------------+---------+-----------+-------+--------+
我想做的是创建一个语句,该语句可以提取 5 天的记录并返回一个结果集,该结果集每天都有一行,其中包含上述所有信息以及每天的平均温度。我知道目前的数据都具有相同的温度,但它是在一个没有任何变化的测试环境中。不是DBA,我有点卡住了。