Update based on field(s)

When using Update Write Mode, Data Fetcher can use unique fields (like an ID field) from your API response to intelligently match and merge data with existing records in your output view. This prevents data from being written to the wrong records and preserves any existing relationships or custom record values.

How to set Update Based on Field(s)

1. Navigate to the request screen in Data Fetcher.

2. Scroll down to the bottom and click to open the Advanced settings.

3. Under Write Mode, ensure Update is selected.

4. Under Update Based on Field(s), select the field from your output table that contains unique values.

5. You can select multiple fields if needed for matching.

Important: Data Fetcher only looks at records in the output view, not the entire output table. If Airtable filters on your output view prevent Data Fetcher from finding matching records, duplicate records will be created instead.

Recommendation: Create a dedicated, locked view with no filters to use as your output view.

Why this matters: A practical example

Let's say your current Airtable output view contains:

Item Id	Item name	Units sold
229	Orange Hat	5
107	Purple Skirt	10

Your API returns this updated data:

Item Id	Item name	Units sold
692	Blue T-Shirt	7
229	Orange Hat	10
107	Purple Skirt	17

Without Update Based on Field(s) (set to None)

Data Fetcher updates records by position, resulting in:

Item Id	Item name	Units sold
692	Blue T-Shirt	7
229	Orange Hat	10
107	Purple Skirt	17

The problem: The first record that was originally linked to "Orange Hat" is now associated with "Blue T-Shirt". Any existing relationships, comments, or custom field values are now tied to the wrong item.

With Update Based on Field(s) (set to 'Item Id')

Data Fetcher matches records using the unique Item Id field, resulting in:

Item Id	Item name	Units sold
229	Orange Hat	10
107	Purple Skirt	17
692	Blue T-Shirt	7

The result: Existing records are properly updated while preserving their identity and relationships. New records are added separately.

When to use Update Based on Field(s)

• Choose a unique field when your API response contains records that should update specific existing records based on a common identifier.

• Choose multiple fields when there is no unique identifier, but a combination of field values will always be unique.

• Set to 'None' when running on multiple records where the position in the Run on Multiple Records table should determine which output record gets updated.