InfluxQL miscellaneous functions

Use InfluxQL miscellaneous functions to perform different operations in InfluxQL queries.

fill()

Fills null field values returned from empty time windows in GROUP BY time() queries with a specified fill value.

Supported only in the GROUP BY clause.

fill(behavior)

Arguments

  • behavior: Defines the behavior of the fill operation. If no FILL clause is included, the default behavior is fill(null).

    The following options are available:

    • numeric literal: Replaces null values with the specified numeric literal.
    • linear: Uses linear interpolation between existing values to replace null values.
    • none: Removes rows with null field values.
    • null: Keeps null values and associated timestamps.
    • previous: Replaces null values with the most recent non-null value.

Examples

The following example uses the Bitcoin price sample dataset.

fill(numeric_literal) fill(linear) fill(none) fill(null) fill(previous)

SELECT
  MEAN(price)
FROM bitcoin
WHERE
  code = 'USD'
  AND time >= '2023-05-01T00:00:00Z'
  AND time < '2023-05-01T02:00:00Z'
GROUP BY
  time(30m)
  fill(0)

name: bitcoin

timemean
2023-05-01T00:00:00Z29319.9092
2023-05-01T00:30:00Z29307.4416
2023-05-01T01:00:00Z0
2023-05-01T01:30:00Z29263.2886
SELECT
  MEAN(price)
FROM bitcoin
WHERE
  code = 'USD'
  AND time >= '2023-05-01T00:00:00Z'
  AND time < '2023-05-01T02:00:00Z'
GROUP BY
  time(30m)
  fill(linear)

name: bitcoin

timemean
2023-05-01T00:00:00Z29319.9092
2023-05-01T00:30:00Z29307.4416
2023-05-01T01:00:00Z29285.3651
2023-05-01T01:30:00Z29263.2886
SELECT
  MEAN(price)
FROM bitcoin
WHERE
  code = 'USD'
  AND time >= '2023-05-01T00:00:00Z'
  AND time < '2023-05-01T02:00:00Z'
GROUP BY
  time(30m)
  fill(none)

name: bitcoin

timemean
2023-05-01T00:00:00Z29319.9092
2023-05-01T00:30:00Z29307.4416
2023-05-01T01:30:00Z29263.2886
SELECT
  MEAN(price)
FROM bitcoin
WHERE
  code = 'USD'
  AND time >= '2023-05-01T00:00:00Z'
  AND time < '2023-05-01T02:00:00Z'
GROUP BY
  time(30m)
  fill(null)

name: bitcoin

timemean
2023-05-01T00:00:00Z29319.9092
2023-05-01T00:30:00Z29307.4416
2023-05-01T01:00:00Z
2023-05-01T01:30:00Z29263.2886
SELECT
  MEAN(price)
FROM bitcoin
WHERE
  code = 'USD'
  AND time >= '2023-05-01T00:00:00Z'
  AND time < '2023-05-01T02:00:00Z'
GROUP BY
  time(30m)
  fill(previous)

name: bitcoin

timemean
2023-05-01T00:00:00Z29319.9092
2023-05-01T00:30:00Z29307.4416
2023-05-01T01:00:00Z29307.4416
2023-05-01T01:30:00Z29263.2886

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