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| contentType: howto |
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| # Mapping in the UI |
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| Data mapping means referencing data from previous nodes. It doesn't include changing (transforming) data, just referencing it. |
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| You can map data in the following ways: |
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| * Using the expressions editor. |
| * By dragging and dropping data from the **INPUT** into parameters. This generates the expression for you. |
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| For information on errors with mapping and linking items, refer to [Item linking errors](/data/data-mapping/data-item-linking/item-linking-errors.md). |
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| ## How to drag and drop data |
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| 1. Run your workflow to load data. |
| 2. Open the node where you need to map data. |
| 3. You can map in table, JSON, and schema view: |
| * In table view: click and hold a table heading to map top level data, or a field in the table to map nested data. |
| * In JSON view: click and hold a key. |
| * In schema view: click and hold a key. |
| 4. Drag the item into the field where you want to use the data. |
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| ### Understand what you're mapping with drag and drop |
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| Data mapping maps the key path, and loads the key's value into the field. For example, given the following data: |
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| ```js |
| [ |
| { |
| "fruit": "apples", |
| "color": "green" |
| } |
| ] |
| ``` |
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| You can map `fruit` by dragging and dropping **fruit** from the **INPUT** into the field where you want to use its value. This creates an expression, `{{ $json.fruit }}`. When the node iterates over input items, the value of the field becomes the value of `fruit` for each item. |
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| ### Understand nested data |
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| Given the following data: |
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| ```js |
| [ |
| { |
| "name": "First item", |
| "nested": { |
| "example-number-field": 1, |
| "example-string-field": "apples" |
| } |
| }, |
| { |
| "name": "Second item", |
| "nested": { |
| "example-number-field": 2, |
| "example-string-field": "oranges" |
| } |
| } |
| ] |
| ``` |
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| n8n displays it in table form like this: |
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