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# FieldMerge

Builds a string from a multi-value databox — an Address question, an HTTP request, or a SQL query returning several columns — by substituting named columns into a pattern.

The pattern names each column in square brackets, and everything else in the pattern is kept as it is.

For a databox holding:

```xml
<KFXmlValue rows="1">
  <KFRow id="0"><userId>1</userId><name>George Smiley</name></KFRow>
</KFXmlValue>
```

| Expression                        | Result              |
| --------------------------------- | ------------------- |
| `FieldMerge("[name] ([userId])")` | `George Smiley (1)` |

Where the databox holds more than one row, `FieldMerge` uses the first row only. To build a string from every row, use [RowMerge](/reference/expression-reference/text-expressions/rowmerge.md).

An expression containing `FieldMerge` on a databox-driven Dynamic List question runs once per option, which makes it a tidy way to format the options in that list.