Adding a formula to the selected column will delete all indexes and relationships it participates in. (Visual Database Tools)
The column you are modifying participates in one or more relationships or contributes to one or more indexes. When you modify the column, it will become a computed column, which cannot participate in relationships or contribute to indexes. Choose Yes to proceed with the operation and delete the indexes and relationships. Choose No to cancel the operation.
See Also
Concepts
Error Messages in Visual Database Tools
Other Resources
Computed Columns
Creating Indexes on Computed Columns