---
title: "Combine Data"
slug: "combine-data"
description: "Data Union in Dataddo: Easily add datasets from multiple sources to a single data flow. Learn how to match schemas, add sources, configure flows & troubleshoot."
updated: 2026-07-11T09:06:17Z
published: 2026-07-11T09:06:17Z
canonical: "docs.dataddo.com/combine-data"
---

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

# Combine Data

The **Combine data** features allows you to merge data from multiple ***data sources*** in a single ***data flow***.

1. Navigate to the **Flows** page and click on [**Create Flow**](https://app.dataddo.com/flow/new).
2. Click on **Connect Your Data Source** and click **Combine Sources** in the top-right.
3. Choose one of the following:
  - [SQL Editor](/docs/combine-data#sql-editor): Use this option for high-volume datasets, complex data transformations, or when you require the flexibility of custom SQL queries to join your data.
  - [Data Union](/docs/combine-data#data-union): Use this option for straightforward use cases where you are merging datasets that already share an identical or highly similar schema without the need for custom logic.

![Data source combination options](https://cdn.document360.io/084ed225-3f99-4644-a2da-39ca0cd5ef45/Images/Documentation/Data%20transformation%202%20-%20Combine%20sources%20options.png)

## SQL Editor

The SQL editor is self-service interface that allows users to write custom SQL queries for joining and merging multiple data sources. It is optimized for high-volume datasets and utilizes internal unique IDs to prevent queries from breaking if data sources or columns are subsequently renamed.

### Add Multiple Sources to a Flow

1. Select **SQL Editor**.
2. Select all the ***sources*** you want to work with.
3. Write your query using the provided table and column names.
4. Click on **Save Source** in the top right corner.
5. Add your ***data destination***, finish configuring your flow, and click on **Save Flow**.

**Use provided table and column names**

Ensure you've **selected** all the ***sources*** you are working with, otherwise the query fails.

![SQL editor](https://cdn.document360.io/084ed225-3f99-4644-a2da-39ca0cd5ef45/Images/Documentation/Data%20transformation%203b%20-%20SQL%20editor.png)

## Data Union

It operates similarly to the `UNION` operator in SQL.

### Prerequisites

When creating your ***sources***, make sure they have **the exact same schemas**, including the same:

- **Number** of columns
- Column **names**/labels
- **Data types**

### Add Multiple Sources to a Flow

1. Select **Data Union**.
2. After you select your first source, only other compatible sources become selectable.
3. Click on **Save Source** in the top right corner.
4. Add your ***data destination***, finish configuring your flow, and click on **Save Flow**.

![Union sources](https://cdn.document360.io/084ed225-3f99-4644-a2da-39ca0cd5ef45/Images/Documentation/Data%20transformation%203a%20-%20Data%20Union.png)

## Troubleshooting

### Maximum Number of Sources

In Dataddo, it is possible to union up to **100 *sources***. If you need to combine more ***sources***, it will be necessary to create multiple flows.

### Different Data Types

To check the data types of your source, click on the three dots, select **Edit** and navigate to the **Data Types** tab. If the data types don’t match (like in this example), you can change the data type of each column.

| Source 1 | Data type |
| --- | --- |
| Column A | **Float** |
| Column B | Integer |

| Source 2 | Data type |
| --- | --- |
| Column A | Integer --> change to **Float** |
| Column B | Integer |

![Change data type](https://cdn.document360.io/084ed225-3f99-4644-a2da-39ca0cd5ef45/Images/Documentation/Schema%20-%20Change%20data%20type.png)

### SQL Query Fails

If your query fails and you're sure the syntax is correct, check the following:

- All the ***sources*** you're working with **are selected** from the sources picker.
- You're using the table and column names as provided in the picker. To see all available column, click the arrow on the left of your ***source***.

A source is a collection of data from an authorized service that's been connected via a Dataddo connector. Data within the source is automatically refreshed based on the source's configuration.

Data flows allow you to orchestrate the integration of your data from various sources to your desired destinations. You may add multiple data sources with the same schema to one flow to merge data for a consolidated output.

A destination is the endpoint where the data from your sources will be loaded. Destinations include dashboarding tools, data warehouses, and other online services.