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 |
|---|---|
| 2021-01-01T00:00:00Z | 1.2 |
| 2021-01-01T02:00:00Z | |
| 2021-01-01T03:00:00Z | 2.5 |
| 2021-01-01T04:00:00Z |
The example above returns:
| _time | _value |
|---|---|
| 2021-01-01T00:00:00Z | 1.2 |
| 2021-01-01T03:00:00Z | 2.5 |
Include null values in an ad hoc stream of tables
- Use
array.from()to create an ad hoc stream of tables. - 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:
| a | b | c | d |
|---|---|---|---|
| 1 | 2 | 3 | four |
| 5 | 6 |
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