Column mappings define the relationship between columns in lists and columns that appear in reports.
The column mapping section also allows you to map a column to another column. There are three main scenarios where you might need to remap a column.
The scenarios where you would need to do this include:
If you have two columns in two different lists that perform the same function, but have different internal names, you can map them to a single column.
For example, the Assigned To column is called AssignedTo in most lists; however, in the Project Deliverable Library, the Assigned To column has an internal name of AssignedToUser.
If you had two columns in two separate lists that had the same name, but actually performed different functions, you could distinguish between them by mapping one of them to a different name - otherwise they will roll up under the same column in the report.
Report column names cannot have a number as a leading character. If a column has a number as a leading character you will have to map it to a column that does not have a number as a leading character (e.g. from 07_Feb_Sales to Feb_Sales_07).
To update the column mappings:
The purpose of the column mappings page is to map columns in the report to columns in the List Query Template. To be able to map a column in a List Query Template you must first add the column to the report.
If you have specified a context, you will be able to select a column from the List menu on the left.
If a column in the list and in the Columns section have the same internal name they will be automatically mapped (you will still have to select the column to include it in the report).
Context Settings enable you to define a list to use to test your CAML and to build the column mappings. It is important that you select a context first as selecting a new one resets the page.
This SharePoint dialog shows 15 items at a time. There is a link in the top-right of the dialog to see the next 15 items. This also applies when selecting the list context.