To replace fields with null values, you must use Data Loader.
- Choose to open Data Loader.
- Click Export and complete the wizard. When the operation finishes, click View Extraction.
- Click Open in external program to open your data in Excel. Blank out the fields you want to update.
- In Data Loader, choose Insert null values. Click OK to save your settings., and select
- Click Update and follow the wizard to reimport your data.