Within data load and dimension build rules files, you can undo field operations (including move, split, join, create using text, and create using join).
Field operations are undone sequentially (from most to least recent).
To undo the most recent field operation, select Edit, and then Undo.
To undo multiple field operations:
Open or create the rules file.
Select Options, and then Data source properties.
In the Data Source Properties dialog box, select the Field Edits tab.
Select the bottom (most recent) operation, and click Delete.
The originally second most recent operation becomes the most recent (bottom) operation.
Repeat step 4 until all operations that you want to undo are deleted.
Click OK.
Related Information
About Field Operations