面试题：InfluxDB中InfluxQL高级查询之结合函数与子查询的复杂场景处理

Question

在InfluxDB中有measurement "sensor_readings"，记录传感器读数，有字段"value"，tag "sensor_id"和"location"。现在需要找出每个位置中传感器读数标准差大于该位置所有传感器读数平均值10%的传感器ID，使用InfluxQL该如何实现？（提示：可能需要结合子查询和相关函数）

Answer 1

SELECT "sensor_id"
FROM (
    SELECT stddev("value") AS "std_dev", mean("value") AS "avg_value"
    FROM "sensor_readings"
    GROUP BY "location", "sensor_id"
) AS subquery
WHERE "std_dev" > 0.1 * "avg_value"