docs-v2/content/v2.0/reference/flux/functions/built-in/transformations/union.md

title	description	aliases	menu	weight
union() function	The `union()` function concatenates two or more input streams into a single output stream.	/v2.0/reference/flux/functions/transformations/union	v2_0_ref name parent union built-in-transformations	401

The union() function concatenates two or more input streams into a single output stream. In tables that have identical schemas and group keys, contents of the tables will be concatenated in the output stream. The output schemas of the union() function is the union of all input schemas.

union() does not preserve the sort order of the rows within tables. A sort operation may be added if a specific sort order is needed.

Function type: Transformation Output data type: Object

union(tables: ["table1", "table2"])

Parameters

tables

Specifies the streams to union together. There must be at least two streams.

Data type: Array of streams

Examples

left = from(bucket: "test")
  |> range(start: 2018-05-22T19:53:00Z, stop: 2018-05-22T19:53:50Z)
  |> filter(fn: (r) =>
    r._field == "usage_guest" or
    r._field == "usage_guest_nice"
  )
  |> drop(columns: ["_start", "_stop"])

right = from(bucket: "test")
  |> range(start: 2018-05-22T19:53:50Z, stop: 2018-05-22T19:54:20Z)
  |> filter(fn: (r) =>
    r._field == "usage_guest" or
    r._field == "usage_idle"
  )
  |> drop(columns: ["_start", "_stop"])

union(tables: [left, right])