> ## 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.

# Union

> Perform addition of rows from multiple tables

export const gemName_0 = "Union"

export const execution_engine_0 = "the SQL warehouse"

<Info>This gem runs in {execution_engine_0}.</Info>

## Overview

The Union gem lets you combine records from different tables for cases such as merging customer databases or aggregating logs from multiple servers.

<Tip>
  The {gemName_0} gem has a corresponding interactive gem example. See [Interactive gem
  examples](/data-analysis/gems/gems#interactive-gem-examples) to learn how to run sample pipelines
  for this and other gems.
</Tip>

## Input and Output

| Port    | Description                                           |
| ------- | ----------------------------------------------------- |
| **in0** | The first input table.                                |
| **in1** | The second input table.                               |
| **inN** | Optional: Additional input tables.                    |
| **out** | A single table containing all rows from input tables. |

To add additional input ports, click `+` next to **Ports**.

All input tables must have **identical schemas** (matching column names and data types). If table columns have different orders or a different number of columns, use the [UnionByName](/data-analysis/gems/join-split/union-by-name) gem.

## Parameters

| Parameter               | Description                                     |
| ----------------------- | ----------------------------------------------- |
| Operation Type          | Shows that the set operation type is `Union`    |
| Preserve duplicate rows | Checkbox to keep duplicates in the output table |

## Example

Let's say you're working with two tables: **Table A** and **Table B**.

* Both tables contain order-related data.
* **Table A** contains order information from customer `1`, `2`, and `3`.
* **Table B** contains order information from customer `1`, `2`, `3`, and `4`.
* These tables contain some identical records (duplicates).

### Table A

<div class="table-example">
  | `order_id` | `customer_id` | `order_date` | `amount` |
  | ---------- | ------------- | ------------ | -------- |
  | 101        | 1             | 2024-12-01   | 250.00   |
  | 102        | 2             | 2024-12-03   | 150.00   |
  | 103        | 1             | 2025-01-15   | 300.00   |
  | 104        | 3             | 2025-02-10   | 200.00   |
</div>

### Table B

<div class="table-example">
  | `order_id` | `customer_id` | `order_date` | `amount` |
  | ---------- | ------------- | ------------ | -------- |
  | 103        | 1             | 2025-01-15   | 300.00   |
  | 104        | 3             | 2025-02-10   | 200.00   |
  | 105        | 4             | 2025-03-05   | 400.00   |
  | 106        | 2             | 2025-03-07   | 180.00   |
</div>

### Result without duplicates

The following is the output table without duplicates.

<div class="table-example">
  | `order_id` | `customer_id` | `order_date` | `amount` |
  | ---------- | ------------- | ------------ | -------- |
  | 101        | 1             | 2024-12-01   | 250.00   |
  | 102        | 2             | 2024-12-03   | 150.00   |
  | 103        | 1             | 2025-01-15   | 300.00   |
  | 104        | 3             | 2025-02-10   | 200.00   |
  | 105        | 4             | 2025-03-05   | 400.00   |
  | 106        | 2             | 2025-03-07   | 180.00   |
</div>

### Result with duplicates

The following is the output table when you select **Preserve duplicate rows** in the gem configuration.

<div class="table-example">
  | `order_id` | `customer_id` | `order_date` | `amount` |
  | ---------- | ------------- | ------------ | -------- |
  | 101        | 1             | 2024-12-01   | 250.00   |
  | 102        | 2             | 2024-12-03   | 150.00   |
  | 103        | 1             | 2025-01-15   | 300.00   |
  | 104        | 3             | 2025-02-10   | 200.00   |
  | 103        | 1             | 2025-01-15   | 300.00   |
  | 104        | 3             | 2025-02-10   | 200.00   |
  | 105        | 4             | 2025-03-05   | 400.00   |
  | 106        | 2             | 2025-03-07   | 180.00   |
</div>

<Tip>Order `103` and `104` are duplicate records.</Tip>