Which key retains its uniqueness even after you remove some of the fields?

The___ retains its uniqueness even after you remove some of the fields.

The Unique constraint/key.

Unique constraints or keys can be used to retain the uniqueness of combinations of fields replaced as a primary key with a generated ID. They enable you enforce 1 - 1 relationship. There may be one Primary Key for one table and many unique key constraints for one table.