For more information about many-to-one mappings see Many-to-one mapping and Transforms that create many-to-one mappings.
To create a new many-to-one mapping:
In the mapping routine area, drag a source element to the target element, as you do when you are creating a one-to-one mapping (see Creating a one-to-one mapping).
The mapping editor creates a one-to-one mapping between the source element and the target element and sets the transform to an appropriate default transform type (see Default transform type).
Drag an additional source element to the transform.
The mapping editor creates a connection between the additional source element and the transform and if necessary resets the transform to an appropriate default transform type.