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# Combine or replace data when new files arrive in a folder

> Choose whether a Data Consolidation adds each new file's rows or replaces the dataset, what happens when column types differ, and how file columns are mapped.
>
> Applies to: Where: New automation › Data Consolidation › Select destination › Combine / Replace Settings

A [Data Consolidation](https://mammoth.io/docs/learn/automate/consolidate/) automation adds each new file in its folder to a destination dataset, using that dataset's own settings. Open them from the pencil next to **Update method** in the wizard's **Select destination** step (tooltip **Combine / Replace Settings for Sales**, with your dataset's name), or set them beforehand on the dataset itself.

## Change the destination's update, type and mapping settings

![20261007_190207_draft_01_learn_automation-creation-editing-moved-from-full-page-routes-to-in-place-modals-with-live-status-and-quick-actions-2_2 (1).png](https://mammoth.io/docs/images/20261008_124829_20261007_190207_draft_01_learn_automation-creation-editing-moved-from-full-page-routes-to-in-place-modals-with-live-status-and-quick-actions-2_21.webp)

The settings note "These changes will be applied to the Dataset settings": they change the dataset itself, not only this automation.

| Setting | Options | What it does |
| --- | --- | --- |
| **Update method** | **Replace all data**, **Add to existing data** | A note says the source data is deleted after combining or replacing |
| **If column type doesn't match** | **Convert destination column to text**, **Convert incompatible values to null**, **Do not update the dataset** | What happens when a file column's type differs from the destination's. Shown once the dataset has had data added |
| **Column Mapping** | **Map with existing columns**, **Create new column mapping** | Map by matching column names, or set your own mapping |

With **Create new column mapping**, each destination column lists the file column names it accepts. Click **+** to add another name (**Add New Column**), turn a column off with its toggle, and tick **All destination columns must be mapped** to take new data only when the column count matches. See [Add or replace data in a dataset](https://mammoth.io/docs/learn/get-data-in/add-or-replace-data/).

## Choose Combine or Replace

| Mode (**Update method**) | Behaviour | Best for |
| --- | --- | --- |
| Combine (**Add to existing data**) | Keeps the existing rows and adds each new file's rows. Data builds up over time | Incremental data: daily transactions, event logs |
| Replace (**Replace all data**) | Swaps the dataset's data for the new file's contents. Previous data is removed | Full snapshots: weekly inventory exports |

## What happens when a file's columns don't match

Before a file goes in, Mammoth checks its columns against the destination, separately from the name pattern: a file can match your pattern and still not fit.

- Column names must match, by display name or by the names in your column mapping.
- Data types must be compatible. Otherwise Mammoth converts the column to text, converts incompatible values to null, or doesn't update the dataset, as **If column type doesn't match** says.

A file with new or missing columns stays in the folder with a reason such as "Has a new column for Sales: Region" or "Its columns don't match Sales". If people upload files with slightly different column names, add those names to the column mapping, or agree on a standard template.

## Related

- [Combine files dropped in a folder into one dataset](https://mammoth.io/docs/learn/automate/consolidate/): set up the automation.
- [Fix files a watched folder didn't add](https://mammoth.io/docs/learn/automate/watched-folder-files/): map the columns of a file that didn't go in.
- [Add or replace data in a dataset](https://mammoth.io/docs/learn/get-data-in/add-or-replace-data/): the update and mapping settings in detail.

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Source: https://mammoth.io/docs/learn/automate/consolidate-settings.md · Updated: 2026-11-08