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

Through the process of sedimentation,sediment is turned back to rock to form sedimentation.the process of sedimentation is: > deposition-where fragments were deposited into the river or sea under gravity or travelling agent such as wind or water. > sedimentation-the fragments deposited in the river sedimented and accumulate> compaction-the layers of fragments deposited undergoes compaction due to the weight if the upper layers> cementation-chemical substance of the fragments such as cement dissolved into the water and cement the other fragments together to form sedimentary rock.thus,cementation and compaction are the process.on the other hand, transformation only occur when a rock under goes metamorphism(compaction or extreme heat).while recrystillization occurs when a rock is melted and cooled down,which also requires metamorphism to take place.hope it !