InfluxQL selector functions

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.

• FIRST()
• LAST()
• MAX()
• MIN()

• Notable behaviors of selector functions

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

SELECT FIRST(*) FROM home

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

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)

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

SELECT LAST(*) FROM home

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

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)

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

SELECT MAX(*) FROM home

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

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)

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

SELECT MIN(*) FROM home

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

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)

Notable behaviors of selector functions

• Timestamps when grouping by time

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.