[英]sql query to get latest data from multiple columns when there are nulls in the data
我有一个看起来像的 sql 表
+--------------------------+------------+-----------------+---------+------+-------+-------------+-------------------------+----------------------------+-------+-------+
| deviceID | date | timestamp | counter | rssi | vavId | nvo_airflow | nvo_air_damper_position | nvo_temperature_sensor_pps | block | floor |
+--------------------------+------------+-----------------+---------+------+-------+-------------+-------------------------+----------------------------+-------+-------+
| fd00::212:4b00:1957:d616 | 2020-02-29 | 12:40:01.513066 | 805 | 91 | 7 | NULL | NULL | 26.49 | NULL | ABCD |
| fd00::212:4b00:1957:d616 | 2020-02-29 | 12:41:01.542272 | 807 | 94 | 5 | NULL | NULL | 26.37 | NULL | ABCD |
| fd00::212:4b00:1957:d616 | 2020-02-29 | 12:43:01.699023 | 811 | 90 | 7 | 50 | NULL | NULL | NULL | ABCD |
| fd00::212:4b00:1957:d616 | 2020-02-29 | 12:46:01.412259 | 817 | 64 | 26 | NULL | NULL | 25.85 | NULL | ABCD |
| fd00::212:4b00:1957:d616 | 2020-02-29 | 12:48:01.576133 | 821 | 91 | 26 | NULL | NULL | 27.54 | NULL | ABCD |
| fd00::212:4b00:1957:d616 | 2020-02-29 | 12:49:01.529593 | 823 | 91 | 7 | 45 | 72 | NULL | NULL | ABCD |
我想编写一个查询,在其中获取所有 vavId 的nvo_airflow,nvo_air_damper_position,nvo_temperature_sensor_pps
的最新非空值(基于时间戳),或者说特定的 vavId 7 。
如果我们考虑 vav 7 它应该返回
nvo_airflow,nvo_air_damper_position,nvo_temperature_sensor_pps, vavId
45,72,26.49
如果没有空值,我可以编写一个获取最新值的查询
"""SELECT t1.deviceId, t1.date, t1.vavId, t1.timestamp, t1.nvo_airflow , t1.nvo_air_damper_position , t1.nvo_temperature_sensor_pps
FROM
(SELECT deviceId, date, nvo_airflow, nvo_air_damper_position, nvo_temperature_sensor_pps, vavId, timestamp, counter from vavData where date=%s and floor=%s) t1
INNER JOIN
(SELECT date,max(timestamp) as timestamp,vavId from vavData where date=%s and floor=%s group by vavId) t2
ON (t1.timestamp = t2.timestamp) order by t1.vavId"""
但我很困惑如何为有一些空值的多列获取最新数据。 有人可以帮我写一个查询吗
SELECT
nvo_airflow,nvo_air_damper_position,nvo_temperature_sensor_pps, vavId
FROM
vavData
WHERE NOT ( nvo_airflow IS NULL
OR nvo_air_damper_position IS NULL
OR nvo_temperature_sensor_pps IS NULL )
ORDER BY `date` DESC, `timestamp` DESC
选择并排序数据where not
将排除具有 NULL 值的列。
此查询将返回所有行,最新的第一行。
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