Mapping Rules 
You can define a mapping rule for every mapped field.
Features
You can define the following mapping rules for the fields:
Values
You use this rule to assign values to the mapped fields. Select the mapped field and assign the possible values. You can enter these values from the tables, predefined values from a domain, or the search help attached to the data elements.
ExampleThe target field ORG_TITLE_KEY in the mapping tool refers to the field Title in the table BP: General data I (BUT000). The mapping tool displays the entries maintained in the Customizing table Forms of Address (Key) (Business Address Services) (TSAD3) for the field ORG_TITLE_KEY.
In Customizing, if the title key is maintained as 0001, which refers to Mr., and the external list contains the value Mister, which must be mapped to the field Title in the business partner, then you can maintain this in the Assign Values table after choosing 0001 from the possible values. You can assign multiple values to a field in the possible values option.
The target field PERS_SEX in the mapping tool can be assigned to one of the following fields in the table BP: General data I (BUT000): XSEXM (Male), XSEXF (Female), or XSEXU (Unknown) On selection and mapping of the field PERS_SEX, blank, 1, or 2 referring to Unknown, Female, and Male are displayed. These values are from the domain BU_SEXID.
End of the example.Constant
You can use this rule to assign constant values to mapping fields that require all the business partners to be created with a constant value irrespective of their corresponding entries in the external list.
ExampleAll business partners that were created using an external list are potentially from the same country, for example, Germany. In this case, the field PERS_COUNTRYISO is mapped and the constant value DE is created for this field.
End of the example.Code
You can maintain the ABAP code for the mapping fields that require data or value conversion before they can be assigned to the appropriate fields during the creation of business partners.
ExampleFor example the target field ORG_FOUND_DATE refers to the field FOUND_DAT of the business partner table BUT000. The date format for this field is YYYYMMDD.
Select this field and choose the ABAP Code option.
The data to be converted is in the import parameter LS_D_DATA. This data is converted by writing ABAP code and then assigned to the export parameter LS_MKTLIST_ORG-ORG_FOUND_DATE. The import parameter remains the same for all the target fields but the export parameter changes depending on the target field selected for mapping.
End of the example.