Documentation

Work with null types

The null type represents a missing or unknown value.

Type name: null

Null syntax

Null types exist in columns of other basic types. Flux does not provide a literal syntax for a null value, however, you can use debug.null() to return a null value of a specified type.

import "internal/debug"

// Return a null string
debug.null(type: "string")

// Return a null integer
debug.null(type: "int")

// Return a null boolean
debug.null(type: "bool")

An empty string ("") is not a null value.

Check if a column value is null

In functions that iterate over rows (such as filter() or map()), use the exists logical operator to check if a column value is null.

Filter out rows with null values
data
    |> filter(fn: (r) => exists r._value)
Given the following input data:
_time_value
2021-01-01T00:00:00Z1.2
2021-01-01T02:00:00Z
2021-01-01T03:00:00Z2.5
2021-01-01T04:00:00Z
The example above returns:
_time_value
2021-01-01T00:00:00Z1.2
2021-01-01T03:00:00Z2.5

Include null values in an ad hoc stream of tables

  1. Use array.from() to create an ad hoc stream of tables.
  2. Use debug.null() to include null column values.
import "array"
import "internal/debug"

array.from(
    rows: [
        {a: 1, b: 2, c: 3, d: "four"},
        {a: debug.null(type: "int"), b: 5, c: 6, d: debug.null(type: "string")}
    ]
)
The example above returns:
abcd
123four
56

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