Negatively Mapped Fields
When you create a Data Map for use in a Manual Import or FTP Import Template, you must define the sequence of the columns in the import file, and "map" each column to the desired field in the database where you want to store that data. As you add columns to the Data Map, the system displays a "Column Number," and automatically populates this counter sequentially.
The system supports the ability to "negatively" map fields by entering a negative number as the Column Number. When you negatively map a field, you're telling the system that you want to populate the specified field in the database, but that you don't expect this value to be present in the import file. Instead, the value is going to come from some place other than the import file. This value could come from:
A static value defined using the "Set Default Value" Advanced Field Option. If you assign this advanced option to a field, you can enter a single value that will be assigned to the selected field, for every record that gets imported.
A dynamic value derived using SQL code that you enter into the "Set Default Value" option. For example, you could derive a date value and populate that date in the selected field, for every record that gets imported.
To negatively map a field, simply enter a negative number as the Column Number, then select the desired field in the database that you want to populate. The actual negative number that you use doesn't really matter, as long as the value is negative.
If defining a fixed-width Data Map, the "Start" and "Length" values for a negatively mapped field should both be set to "0."