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Use selector functions to assess, select, and return values in your data. Selector functions return one or more rows with the selected values from each InfluxQL group.

Examples use the sample data set provided in the Get started with InfluxDB tutorial.

BOTTOM()
FIRST()
LAST()
MAX()
MIN()
PERCENTILE()
TOP()
Notable behaviors of selector functions

[!Important]

Missing InfluxQL functions

Some InfluxQL functions are in the process of being rearchitected to work with the InfluxDB 3 storage engine. If a function you need is not here, check the InfluxQL feature support page for more information.

BOTTOM()

Returns the smallest N field values. BOTTOM() supports int64 and float64 field value data types.

BOTTOM(field_expression[, tag_expression_1[, ..., tag_expression_n]], N)

[!Note] Note: BOTTOM() returns the field value with the earliest timestamp if there's a tie between two or more values for the smallest value.

Arguments

field_expression: Expression to identify the field to operate on. Can be a field key or constant.
tag_expression: Expression to identify a tag key to segment by. Can be a tag key or constant. Comma-delimit multiple tags.
N: Number of results to return from each InfluxQL group or specified tag segment.

Notable behaviors

BOTTOM() maintains original timestamps when grouping by time.
BOTTOM() may return fewer points than expected.

Examples

SELECT BOTTOM(temp, 3) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}} {{% influxdb/custom-timestamps %}}

time	bottom
2022-01-01T08:00:00Z	21
2022-01-01T08:00:00Z	21.1
2022-01-01T09:00:00Z	21.4

{{% expand "Select the bottom field value for two unique tag values" %}}

SELECT BOTTOM(temp, room, 2) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}} {{% influxdb/custom-timestamps %}}

time	bottom	room
2022-01-01T08:00:00Z	21	Kitchen
2022-01-01T08:00:00Z	21.1	Living Room

{{% expand "Select the bottom three field values and the tag value associated with each" %}}

SELECT BOTTOM(temp, 3), room FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}} {{% influxdb/custom-timestamps %}}

time	bottom	room
2022-01-01T08:00:00Z	21	Kitchen
2022-01-01T08:00:00Z	21.1	Living Room
2022-01-01T09:00:00Z	21.4	Living Room

{{% expand "Select the bottom field values for unique tag values and within time windows (grouped by time)" %}}

SELECT
  BOTTOM(temp, room, 2)
FROM home
WHERE
  time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T12:00:00Z'
GROUP BY time(2h)

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	bottom	room
2022-01-01T08:00:00Z	21	Kitchen
2022-01-01T08:00:00Z	21.1	Living Room
2022-01-01T10:00:00Z	21.8	Living Room
2022-01-01T11:00:00Z	22.4	Kitchen
2022-01-01T12:00:00Z	22.2	Living Room
2022-01-01T12:00:00Z	22.5	Kitchen

Notice that when grouping by time, BOTTOM() maintains the point's original timestamp.

FIRST()

Returns the field value with the oldest timestamp.

FIRST(field_expression)

Arguments

field_expression: Expression to identify one or more fields to operate on. Can be a field key, constant, regular expression, or wildcard (*). Supports all field data types.

Notable behaviors

FIRST() overrides original timestamps when grouping by time

Examples

SELECT FIRST(temp) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	first
2022-01-01T08:00:00Z	21.1

SELECT FIRST(*) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	first_co	first_hum	first_temp
1970-01-01T00:00:00Z	0	35.9	21.1

{{% expand "Select the first value from field keys that match a regular expression" %}}

SELECT FIRST(/^[th]/) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	first_hum	first_temp
1970-01-01T00:00:00Z	35.9	21.1

{{% expand "Select the first value from a field within time windows (grouped by time)" %}}

SELECT
  FIRST(temp)
FROM home 
WHERE
  room = 'Kitchen'
  AND time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T20:00:00Z'
GROUP BY time(6h)

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	first
2022-01-01T06:00:00Z	21
2022-01-01T12:00:00Z	22.5
2022-01-01T18:00:00Z	23.3

Notice that when grouping by time, FIRST() overrides the point's original timestamp.

LAST()

Returns the field value with the most recent timestamp.

LAST(field_expression)

Arguments

field_expression: Expression to identify one or more fields to operate on. Can be a field key, constant, regular expression, or wildcard (*). Supports all field data types.

Notable behaviors

LAST() overrides original timestamps when grouping by time

Examples

SELECT LAST(temp) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	last
2022-01-01T20:00:00Z	22.7

SELECT LAST(*) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	last_co	last_hum	last_temp
1970-01-01T00:00:00Z	26	36.5	22.7

{{% expand "Select the last value from field keys that match a regular expression" %}}

SELECT LAST(/^[th]/) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	last_hum	last_temp
1970-01-01T00:00:00Z	36.5	22.7

{{% expand "Select the last value from a field within time windows (grouped by time)" %}}

SELECT
  LAST(temp)
FROM home 
WHERE
  room = 'Kitchen'
  AND time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T20:00:00Z'
GROUP BY time(6h)

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	last
2022-01-01T06:00:00Z	22.4
2022-01-01T12:00:00Z	22.7
2022-01-01T18:00:00Z	22.7

Notice that when grouping by time, LAST() overrides the point's original timestamp.

MAX()

Returns the greatest field value.

MAX(field_expression)

Arguments

field_expression: Expression to identify one or more fields to operate on. Can be a field key, constant, regular expression, or wildcard (*). Supports numeric fields.

Notable behaviors

MAX() overrides original timestamps when grouping by time.

Examples

SELECT MAX(co) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	max
2022-01-01T20:00:00Z	26

SELECT MAX(*) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	max_co	max_hum	max_temp
1970-01-01T00:00:00Z	26	36.9	23.3

{{% expand "Select the maximum value from field keys that match a regular expression" %}}

SELECT MAX(/^[th]/) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	max_hum	max_temp
1970-01-01T00:00:00Z	36.9	23.3

{{% expand "Select the maximum value from a field within time windows (grouped by time)" %}}

SELECT
  MAX(temp)
FROM home
WHERE
  room = 'Kitchen'
  AND time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T20:00:00Z'
GROUP BY time(6h)

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	max
2022-01-01T06:00:00Z	23
2022-01-01T12:00:00Z	22.8
2022-01-01T18:00:00Z	23.3

Notice that when grouping by time, MAX() overrides the point's original timestamp.

MIN()

Returns the lowest field value.

MIN(field_expression)

Arguments

field_expression: Expression to identify one or more fields to operate on. Can be a field key, constant, regular expression, or wildcard (*). Supports numeric fields.

Notable behaviors

MIN() overrides original timestamps when grouping by time.

Examples

SELECT MIN(temp) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	min
2022-01-01T08:00:00Z	21

SELECT MIN(*) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	min_co	min_hum	min_temp
1970-01-01T00:00:00Z	0	35.9	21

{{% expand "Select the minimum value from field keys that match a regular expression" %}}

SELECT MIN(/^[th]/) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	min_hum	min_temp
1970-01-01T00:00:00Z	35.9	21

{{% expand "Select the minimum value from a field within time windows (grouped by time)" %}}

SELECT
  MIN(temp)
FROM home
WHERE
  room = 'Kitchen'
  AND time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T20:00:00Z'
GROUP BY time(6h)

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	min
2022-01-01T06:00:00Z	21
2022-01-01T12:00:00Z	22.4
2022-01-01T18:00:00Z	22.7

Notice that when grouping by time, MIN() overrides the point's original timestamp.

PERCENTILE()

Returns the Nth percentile field value.

PERCENTILE(field_expression, N)

Arguments

field_expression: Expression to identify one or more fields to operate on. Can be a field key, constant, regular expression, or wildcard (*). Supports numeric fields.
N: Percentile to return. Must be an integer or float value greater than 0 and less than or equal to 100.

Notable behaviors

PERCENTILE() overrides original timestamps when grouping by time.
PERCENTILE(example_field, 100) is equivalent to MAX(example_field).
PERCENTILE(example_field, 50) is nearly equivalent to MEDIAN(example_field), except MEDIAN() returns the average of the two middle values if the field contains an even number of values.
PERCENTILE(example_field, 0) returns null.

Examples

SELECT PERCENTILE(temp, 50) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	percentile
2022-01-01T11:00:00Z	22.4

{{% expand "Select the 50th percentile value from each field" %}}

SELECT PERCENTILE(*, 50) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	percentile_co	percentile_hum	percentile_temp
1970-01-01T00:00:00Z	1	36	22.4

{{% expand "Select the 50th percentile value from field keys that match a regular expression" %}}

SELECT PERCENTILE(/^[th]/, 50) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	percentile_hum	percentile_temp
1970-01-01T00:00:00Z	36	22.4

{{% expand "Select the 50th percentile value from a field within time windows (grouped by time)" %}}

SELECT
  PERCENTILE(temp, 50)
FROM home
WHERE
  room = 'Kitchen'
  AND time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T20:00:00Z'
GROUP BY time(6h)

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	percentile
2022-01-01T06:00:00Z	22.4
2022-01-01T12:00:00Z	22.7
2022-01-01T18:00:00Z	23.1

Notice that when grouping by time, PERCENTILE() overrides the point's original timestamp.

TOP()

Returns the greatest N field values. TOP() supports int64 and float64 field value data types.

TOP(field_expression[, tag_expression_1[, ..., tag_expression_n]], N)

[!Note] Note: TOP() returns the field value with the earliest timestamp if there's a tie between two or more values for the greatest value.

Arguments

field_expression: Expression to identify the field to operate on. Can be a field key or constant.
tag_expression: Expression to identify a tag key to segment by. Can be a tag key or constant. Comma-delimit multiple tags.
N: Number of results to return from each InfluxQL group or specified tag segment.

Notable behaviors

TOP() maintains original timestamps when grouping by time.
TOP() may return fewer points than expected.

Examples

SELECT TOP(temp, 3) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}} {{% influxdb/custom-timestamps %}}

time	top
2022-01-01T09:00:00Z	23
2022-01-01T18:00:00Z	23.3
2022-01-01T19:00:00Z	23.1

{{% expand "Select the top field value for two unique tag values" %}}

SELECT TOP(temp, room, 2) FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}} {{% influxdb/custom-timestamps %}}

time	top	room
2022-01-01T18:00:00Z	23.3	Kitchen
2022-01-01T18:00:00Z	22.8	Living Room

{{% expand "Select the top three field values and the tag value associated with each" %}}

SELECT TOP(temp, 3), room FROM home

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}} {{% influxdb/custom-timestamps %}}

time	top	room
2022-01-01T09:00:00Z	23	Kitchen
2022-01-01T18:00:00Z	23.3	Kitchen
2022-01-01T19:00:00Z	23.1	Kitchen

{{% expand "Select the top field values for unique tag values and within time windows (grouped by time)" %}}

SELECT
  TOP(temp, room, 2)
FROM home
WHERE
  time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T12:00:00Z'
GROUP BY time(2h)

{{% influxql/table-meta %}} name: home {{% /influxql/table-meta %}}

time	top	room
2022-01-01T09:00:00Z	23	Kitchen
2022-01-01T09:00:00Z	21.4	Living Room
2022-01-01T10:00:00Z	22.7	Kitchen
2022-01-01T11:00:00Z	22.2	Living Room
2022-01-01T12:00:00Z	22.5	Kitchen
2022-01-01T12:00:00Z	22.2	Living Room

Notice that when grouping by time, TOP() maintains the point's original timestamp.

Notable behaviors of selector functions

Timestamps when grouping by time
Selector functions may return fewer points than expected

Timestamps when grouping by time

When using selector functions with a GROUP BY time() clause, most selector functions return the timestamp of the starting boundary for each time interval. However functions with an N argument that specifies the number of results to return per group maintain the original timestamp of each returned point.

Return the start time of each time interval

FIRST()
LAST()
MAX()
MIN()
PERCENTILE()

Selector functions may return fewer points than expected

Queries that use the following selector functions with an N argument may return fewer points than expected.

BOTTOM()
TOP()

If the InfluxQL group or specified tag key contains X points or unique tag values and X is less than N, the function returns X results instead of N for each group or tag value.

The example below selects the bottom 5 temperatures from the Kitchen between {{% influxdb/custom-timestamps-span %}}2022-01-01T08:00:00Z{{% /influxdb/custom-timestamps-span %}} and {{% influxdb/custom-timestamps-span %}}2022-01-01T10:00:00Z{{% /influxdb/custom-timestamps-span %}}. There are only 3 points recorded for the Kitchen during the queried time range, so the query returns 3 points instead of 5.

SELECT BOTTOM(temp, 5)
FROM home
WHERE
  time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T10:00:00Z'
  AND room = 'Kitchen'

time	bottom
2022-01-01T08:00:00Z	21
2022-01-01T09:00:00Z	23
2022-01-01T10:00:00Z	22.7

The example below selects the top temperature from 3 unique values of the room tag. However, the room tag only has 2 unique values, so results only contain 2 values.

SELECT TOP(temp, room, 3) FROM home

time	top	room
2022-01-01T18:00:00Z	23.3	Kitchen
2022-01-01T18:00:00Z	22.8	Living Room

26 KiB Raw Permalink Blame History

Missing InfluxQL functions

BOTTOM()

Arguments

Notable behaviors

Examples

FIRST()

Arguments

Notable behaviors

Examples

LAST()

Arguments

Notable behaviors

Examples

MAX()

Arguments

Notable behaviors

Examples

MIN()

Arguments

Notable behaviors

Examples

PERCENTILE()

Arguments

Notable behaviors

Examples

TOP()

Arguments

Notable behaviors

Examples

Notable behaviors of selector functions

Timestamps when grouping by time

Return the start time of each time interval

Maintain the original timestamp

Selector functions may return fewer points than expected

26 KiB

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