Within data load or dimension build rules files, you can create fields by joining other fields.
To create a field by joining multiple fields:
Select Field, then Create using join.
In the Create Field Using Join dialog box, in Fields to join for create, select two or more fields.
Click OK.
The new field is displayed to the left of the first field in the join.
“Creating a New Field by Joining Fields” in the Oracle Essbase Database Administrator's Guide
Copying Fields