---
title: promql.join() function
description: promql.join() joins two streams of tables on the group key and _time column. See experimental.join.
url: https://docs.influxdata.com/flux/v0/stdlib/internal/promql/join/
estimated_tokens: 639
product: Flux
version: v0
---

# promql.join() function

-   Flux 0.47.0+
-   View InfluxDB support

`promql.join()` joins two streams of tables on the **group key and `_time` column**. See [`experimental.join`](/flux/v0/stdlib/experimental/join/).

**Important**: The `internal/promql` package is not meant for external use.

##### Function type signature

```js
(fn: (left: A, right: B) => C, left: stream[A], right: stream[B]) => stream[C] where A: Record, B: Record, C: Record
```

For more information, see [Function type signatures](/flux/v0/function-type-signatures/).

## Parameters

### left

(Required) First of two streams of tables to join.

### right

(Required) Second of two streams of tables to join.

### fn

(Required) Function with left and right arguments that maps a new output record using values from the `left` and `right` input records. The return value must be a record.