InfluxDB中未搭配聚合函数的GROUP BY查询为何能成功执行？

Great question! This might feel counterintuitive if you're coming from standard SQL, but it's a deliberate design choice in InfluxDB's query language (InfluxQL). Let's break down exactly why your query works:

• InfluxQL has relaxed GROUP BY rules for time series data
  Unlike standard SQL, which enforces that every non-aggregated column in your SELECT clause must be included in the GROUP BY clause, InfluxQL handles this differently. When you group by a tag (like NAME here, which is almost certainly a tag given typical InfluxDB schemas), InfluxDB automatically applies an implicit LAST() aggregate function to all fields in your SELECT * statement. In short, it returns the most recent value of each field for every unique group defined by NAME.

• The FILL(null) clause doesn't impact query validity
  Your FILL(null) parameter is just instructing InfluxDB how to handle gaps in the result set (though since you're grouping by a tag rather than time, its effect is minimal here). It doesn't change the core logic of how GROUP BY works in InfluxQL—it only modifies how missing values are displayed.

• Tag-based grouping is optimized for time series use cases
  InfluxDB is built specifically for time series data, where grouping by tags (like device names, locations, or categories) is a common operation. The implicit aggregation behavior is a convenience: instead of writing SELECT NAME, LAST(field1), LAST(field2) ..., you can use SELECT * to quickly get the latest state of each field per tag group.

To put it in concrete terms: if your sampleTable has a tag NAME and fields like temperature and humidity, your query would return the last recorded temperature and humidity values for each unique NAME in the table.

内容的提问来源于stack exchange，提问作者cSharma