# Example of missing or unwanted data when combining or separating fields

In a data mapping, you might need to identify missing or unwanted data when a source or target field contains compound data. For example, consider a `long_address` field that has this format:

number street apartment city state zip zip+4 country

Suppose that you want to separate the `long_address` field into discrete fields for `number`, `street`, `city`, `state`, and `zip`. To do this, you select `long_address` as the source field and then select the target fields. You then add padding fields at the locations for the parts of the source field that you do not want. In this example, the unwanted parts are apartment, zip+4, and country.

To identify the unwanted parts, you need to know the order of the parts. The order indicates an index for each part of the content in the compound field. For example, the `long_address` field has 8 ordered parts. Starting at 1, the index of each part is:

1 | number
2 | street
3 | apartment
4 | city
5 | state
6 | zip
7 | zip+4
8 | country

In the data mapper, to identify apartment, zip+4, and country as missing, you add padding fields at indexes 3, 7, and 8. See [separate-one-source-field-into-multiple-target-fields].

Now suppose that you want to combine source fields for `number`, `street`, `city`, `state`, and `zip` into a `long_address` target field. Further suppose that there are no source fields to provide content for apartment, zip+4, and country. In the data mapper, you need to identify these fields as missing. Again, you add padding fields at indexes 3, 7, and 8. See [combine-multiple-source-fields-into-one-target-field].