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docs-v2/content/shared/sql-reference/functions/misc.md

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The {{< product-name >}} SQL implementation supports the following miscellaneous functions for performing a variety of operations:

arrow_cast

Casts a value to a specific Arrow data type.

arrow_cast(expression, datatype)

Arguments

  • expression: Expression to cast. Can be a constant, column, or function, and any combination of arithmetic or string operators.
  • datatype: Arrow data type to cast to.

{{< expand-wrapper >}} {{% expand "View arrow_cast query example" %}}

The following example uses the sample data set provided in Get started with InfluxDB tutorial.

SELECT
  arrow_cast(time, 'Int64') AS time,
  arrow_cast(temp, 'Utf8') AS temp,
  arrow_cast(co, 'Float64')AS co
FROM home
LIMIT 1
time temp co
1641024000000000000 21.0 0

{{% /expand %}} {{< /expand-wrapper >}}

arrow_typeof

Returns the underlying Arrow data type of the expression:

arrow_typeof(expression)

Arguments

  • expression: Expression to evaluate. Can be a constant, column, or function, and any combination of arithmetic or string operators.

{{< expand-wrapper >}} {{% expand "View arrow_typeof query example" %}}

The following example uses the sample data set provided in Get started with InfluxDB tutorial.

SELECT
  arrow_typeof(time) AS time,
  arrow_typeof(room) AS room,
  arrow_typeof(temp) AS temp,
  arrow_typeof(co) AS co
FROM home
LIMIT 1
time room temp co
Timestamp(Nanosecond, None) Dictionary(Int32, Utf8) Float64 Int64

{{% /expand %}} {{< /expand-wrapper >}}

get_field

Returns a field from a map or a struct with the specified key.

[!Note] Typically, get_field is indirectly invoked via field access syntax such as my_struct['field_name'] which results in the call: get_field(my_struct, 'field_name').

get_field(collection, field)

Arguments

  • collection: The map or struct to retrieve a field from.
  • field: The name of field the field to retrieve from the map or struct. Must evaluate to a string.

{{< expand-wrapper >}} {{% expand "View get_field example with a struct column" %}}

SELECT
  get_field(influxdb_struct, 'version') AS influxdb_version
FROM
  (VALUES (struct('influxdb' AS product, 'v1' AS version)),
          (struct('influxdb' AS product, 'v2' AS version)),
          (struct('influxdb' AS product, 'v3' AS version))
  ) AS data(influxdb_struct)
influxdb_version
v1
v2
v3

{{% /expand %}} {{% expand "View get_field example with a map column" %}}

SELECT
  get_field(influxdb_map, 'version') AS influxdb_version
FROM
  (VALUES (map {'product': 'influxdb', 'version': 'v1'}),
          (map {'product': 'influxdb', 'version': 'v2'}),
          (map {'product': 'influxdb', 'version': 'v3'})
  ) AS data(influxdb_map)
influxdb_version
v1
v2
v3

{{% /expand %}} {{< /expand-wrapper >}}

interpolate

Fills null values in a specified aggregated column by interpolating values from existing values. Must be used with date_bin_gapfill.

interpolate(aggregate_expression)

Arguments

  • aggregate_expression: Aggregate operation on a specified expression. The operation can use any aggregate function. The expression can be a constant, column, or function, and any combination of arithmetic operators supported by the aggregate function.
Related functions

date_bin_gapfill, locf

{{< expand-wrapper >}} {{% expand "View interpolate query example" %}}

The following example uses the sample data set provided in the Get started with InfluxDB tutorial.

{{% influxdb/custom-timestamps %}}

SELECT
  date_bin_gapfill(INTERVAL '30 minutes', time) as _time,
  room,
  interpolate(avg(temp))
FROM home
WHERE
    time >= '2022-01-01T08:00:00Z'
    AND time <= '2022-01-01T10:00:00Z'
GROUP BY _time, room
_time room AVG(home.temp)
2022-01-01T08:00:00Z Kitchen 21
2022-01-01T08:30:00Z Kitchen 22
2022-01-01T09:00:00Z Kitchen 23
2022-01-01T09:30:00Z Kitchen 22.85
2022-01-01T10:00:00Z Kitchen 22.7
2022-01-01T08:00:00Z Living Room 21.1
2022-01-01T08:30:00Z Living Room 21.25
2022-01-01T09:00:00Z Living Room 21.4
2022-01-01T09:30:00Z Living Room 21.6
2022-01-01T10:00:00Z Living Room 21.8

{{% /influxdb/custom-timestamps %}}

{{% /expand %}} {{< /expand-wrapper >}}

locf

Fills null values in a specified aggregated column by carrying the last observed value forward. Must be used with date_bin_gapfill.

LOCF is an initialism of "last observation carried forward."

locf(aggregate_expression)

Arguments

  • aggregate_expression: Aggregate operation on a specified expression. The operation can use any aggregate function. The expression can be a constant, column, or function, and any combination of arithmetic operators supported by the aggregate function.
Related functions

date_bin_gapfill, interpolate

{{< expand-wrapper >}} {{% expand "View locf query example" %}}

The following example uses the sample data set provided in the Get started with InfluxDB tutorial.

{{% influxdb/custom-timestamps %}}

SELECT
  date_bin_gapfill(INTERVAL '30 minutes', time) as _time,
  room,
  locf(avg(temp))
FROM home
WHERE
    time >= '2022-01-01T08:00:00Z'
    AND time <= '2022-01-01T10:00:00Z'
GROUP BY _time, room
_time room AVG(home.temp)
2022-01-01T08:00:00Z Kitchen 21
2022-01-01T08:30:00Z Kitchen 21
2022-01-01T09:00:00Z Kitchen 23
2022-01-01T09:30:00Z Kitchen 23
2022-01-01T10:00:00Z Kitchen 22.7
2022-01-01T08:00:00Z Living Room 21.1
2022-01-01T08:30:00Z Living Room 21.1
2022-01-01T09:00:00Z Living Room 21.4
2022-01-01T09:30:00Z Living Room 21.4
2022-01-01T10:00:00Z Living Room 21.8

{{% /influxdb/custom-timestamps %}}

{{% /expand %}} {{< /expand-wrapper >}}

version

Returns the version of DataFusion.

version()