TL;DR InfluxDB Tech Tips - InfluxQL Query Examples

By Jimmy Guerrero / Developer
Jul 07, 2016

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In this post we recap the week’s most interesting influxQL query examples, InfluxDB and TICK-stack related issues, workarounds, how-tos and Q&A from GitHub, IRC and the InfluxDB Google Group that you might have missed.

Understanding unexpected fill() behavior

Q: I’m using fill(0) in my query but it doesn’t return any results. Is this the expected behavior?

A: If none of your data fall within your query’s time range, your query will return no results - even if your query includes fill(). This is how fill() currently works but there is an open issue to change that behavior.

For example:

Write one data point:

> INSERT invisible person=7 1467842220000000000
> SELECT * FROM "invisible"
name: invisible
---------------
time                   person
2016-07-06T21:57:00Z   7

Use fill(0) and query a time range that includes the point:

> SELECT mean("person") FROM "invisible" WHERE time >= '2016-07-06T21:57:00Z' AND time <= '2016-07-06T21:59:00Z' GROUP BY time(1m) fill(0)
name: invisible
---------------
time                   mean
2016-07-06T21:57:00Z   7
2016-07-06T21:58:00Z   0
2016-07-06T21:59:00Z   0

Use fill(0) and query a time range that doesn’t include the point:

> SELECT mean("person") FROM "invisible" WHERE time >= '2016-07-06T21:58:00Z' AND time <= '2016-07-06T21:59:00Z' GROUP BY time(1m) fill(0)

Querying for the latest point in a measurement

Q: I’m trying to find the last point in my measurement. I’ve included the query that I use to do that, but I’m wondering - is there a better way to do this?

> SELECT "dance_id" FROM "ballroom" ORDER BY time DESC LIMIT 1
name: ballroom
--------------
time                   dance_id
2016-07-06T20:26:10Z   103

A: Yes! There’s an InfluxQL function (LAST()) that returns the last point in a measurement:

> SELECT last("dance_id") FROM "ballroom"
name: ballroom
--------------
time                   last
2016-07-06T20:26:10Z   103

InfluxDB Tech Tips Video

Check out the video below from the June 2016 InfluxDB Meetup for tips on series cardinality, INTO queries, and more.

For more InfluxDB tips, see our Frequently Asked Questions page and feel free to post your questions in the InfluxDB users group.

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