There are a number of options to map data in the Data Mapping workbooks. You can use the Expression or Lookup columns, but only one method can be used per target field. It is important to review all options to determine what works best for your situation. These two options are configured in each of the Mapping sheets below.
Expression
The Expression column can be used to directly map fields with compatible data types. Some source and target fields are automatically matched if they have the same field names. For example, Type in the TargetField column will be directly mapped from Type in the source dataset using the Expression column as shown below. It is always good to review any automatically matched fields to verify that the source and target data types match, and if coded domains are present, that the values are equivalent.
The Expression column can also be customized to use Python code written directly in Excel or to call out a function found in the Scripts folder. The following are example scenarios in which this is the best option: changing the data type of a field during in-process translation, mapping all source values into one target value, or creating a globally unique identifier (GUID).
Lookup columns
Use the LookupSheet, LookupKeys, and LookupValue columns when fields have domains that differ between source and target. In the LookupSheet column, enter the name of one of the blue domain sheets. This provides the correct reference to the location of the domains. In the LookupKeys column, specify one or more columns to be searched within the domain sheet. Finally, fill in the LookupValue column to relate the values to the correct target location. The following image shows how to use the Lookup columns to map a set of values to a single field: 