You're right - here's a short example: Raw data:
> SELECT * FROM m name: m time f1 f2 ---- ---- ---- 2016-11-30T17:16:09Z 1 12 2016-11-30T17:16:30Z 4 34 2016-11-30T17:18:29Z 56 The query below returns the last value of f1 and the value of f2 at that time. You can see this in the column headers - the header for last value of f1 is last and the header for the value of f2 is f2. > SELECT last(f1),f2 from m name: m time last f2 ---- ---- ---- 2016-11-30T17:16:30Z 4 34 The query below returns the last value of f1 and the last value of f2, independent of the last value of f1. InfluxDB returns 1970-01-01T00:00:00Z (the null timestamp equivalent) as the timestamp because it can't return two different timestamps for the same point. > SELECT last(f1),last(f2) from m name: m time last last_1 ---- ---- ------ 1970-01-01T00:00:00Z 4 56 I hope this helps. We're working on re-doing the functions page so I'll add this to the issue <https://github.com/influxdata/docs.influxdata.com/issues/757>. And yes, adding a time constraint in the WHERE clause should help a bit in 1.1, but it's not as necessary as it was in 1.0. On Tuesday, November 29, 2016 at 6:39:31 AM UTC-8, [email protected] wrote: > > I wanted to confirm the behavior of LAST() to make sure I'm not relying on > something undocumented or likely to change. Because I couldn't find this in > the docs. > > If I do: > > SELECT LAST(f1), f2 FROM m > > I am getting the last value of f1, say at time T, and the value of f2 ALSO > AT TIME T. > > If I do: > > SELECT LAST(f1), LAST(f2) from m > > I am getting the last value of f1, say at time T1, and the last value of > f2, which could be at time T2 ... ie, independently. > > Also, in the latest version (1.1), does it improve the performance to add > a time-restricting where clause? I.e, 'WHERE time > now() - 1h' > > Thanks! > > -- Remember to include the version number! --- You received this message because you are subscribed to the Google Groups "InfluxData" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/influxdb. To view this discussion on the web visit https://groups.google.com/d/msgid/influxdb/c4976f3b-9b3d-48e8-aeff-21206681f402%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
