A referential integrity database refactoring is a change which ensures that a referenced row exists within another table and/or that ensures that a row which is no longer needed is removed appropriately so as to improve your database design without changing its semantics.

Refactoring	Example
Add Foreign Key Constraint. Add a foreign key constraint to an existing table to enforce a relationship to another table.
Add Trigger For Calculated Column. Introduce a new trigger to update the value contained in a calculated column.
Drop Foreign Key Constraint. Remove a foreign key constraint from an existing table so that a relationship to another table is no longer enforced by the database.
Introduce Cascading Delete. Ensure that the database automatically deletes the appropriate "child records" when a "parent record" is deleted.
Introduce Hard Delete. Remove an existing column which indicates that a row has been deleted and instead actually delete the row.
Introduce Soft Delete. Introduce a flag to an existing table which indicates that a row has been deleted instead of actually deleting the row.
Introduce Trigger for History. Introduce a new trigger to capture data changes for historical or audit purposes.