> ## Documentation Index
> Fetch the complete documentation index at: https://docs.prophecy.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Alteryx Append Fields tool > Prophecy Join gem

> Mapping between Alteryx’s Append Fields tool and the Prophecy Join gem

The [Alteryx Append Fields tool](https://help.alteryx.com/current/en/designer/tools/join/append-fields-tool.html) attaches every row from one dataset to every row of another.

Prophecy implements equivalent behavior using the [Join gem](/data-analysis/gems/join-split/join).

## Automated migration results

When Import encounters an Alteryx Append tool, it recreates the behavior using a Join gem.

Although the Alteryx Append tool behaves like a Cartesian join, Import does not emit a literal `CROSS JOIN`. Instead, it generates SQL that attaches the selected fields from the secondary input to each row of the primary input using a controlled join pattern. This approach avoids optimizer restrictions associated with explicit `CROSS JOIN`, preserves field-selection semantics, and ensures consistent behavior.

* Prophecy generates a Join gem that combines the target and source streams.
* The Join is configured with a constant condition (`1 = 1`), effectively performing a cross join between the two inputs.
* All columns from both inputs are preserved (`in0.*` and `in1.*`), so each record from one stream is replicated for every record in the other stream, matching Alteryx Append semantics.
* The resulting dataset is then available as a single downstream output in the Prophecy pipeline.

## Manually replicate in Prophecy

1. Add a **Join** gem configured as a **Cross Join**.
2. Connect two datasets to the **Join** gem.
3. Preview results in the Data Explorer.

## Configuration options

### Alteryx Append Fields tool

* Attach the **Target** and **Source** streams to the **Append Fields** tool.
* Optionally, deselect any Source fields you do not want replicated onto each Target row.

### Prophecy Join gem

Attach two datasets to a Join gem configured as a **Cross Join**.

## Output behavior

Alteryx produces a dataset where all combination pairs (Cartesian) or matched rows (key-based) are appended.

Prophecy outputs combined rows that match Alteryx's logical intent.

## Known caveats

* Target and Source ports do not appear in Prophecy.
* Prophecy often imports cross-joins as joins on a constant condition (such as `1 = 1`). This is an explicit representation of a cross join, and is used to preserve semantics and lineage while stabilizing planner behavior. The resulting data is identical to Alteryx’s no-key join or append behavior.
* Cross joins can grow extremely large; ensure datasets are appropriately sized.

## Example

**Goal:** Add a simple `product_category` dataset to every record in a `daily_ production` log.

### Alteryx Append tool example

1. Add an **Append** tool to the canvas.
2. Connect the `daily_production` dataset to the **T** (target) anchor.
3. Connect the `product_category` dataset to the **S** (source) anchor.

### Prophecy example

In Prophecy, this operation is represented using a Join-based pattern that adds the selected fields from the secondary dataset to each row of the primary dataset.

To reproduce this manually in Prophecy:

1. Add a **Join** gem configured as a **Cross Join**.
2. Connect the `daily_production` and `product_category` datasets to the **Join** gem.

The output contains all rows from the primary dataset with the selected source fields appended.