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edits
Changes
→Database Normalization
When an attempt is made to modify (update, insert into, or delete from) a relation, the following undesirable side-effects may arise in relations that have not been sufficiently normalized:
* '''Update anomaly'''. The same information can be expressed on multiple rows; therefore updates to the relation may result in logical inconsistencies.
* '''Insertion anomaly'''. There are circumstances in which certain facts cannot be recorded at all. For example, each record in a "Faculty and Their Courses" relation might contain a Faculty ID, Faculty Name, Faculty Hire Date, and Course Code. Therefore, we can record the details of any faculty member who teaches at least one course, but we cannot record a newly hired faculty member who has not yet been assigned to teach any courses, except by setting the Course Code to null. This phenomenon is known as an insertion anomaly. :[[File:ClipCapIt-181007-123437.PNG]]
* '''Deletion anomaly'''. Under certain circumstances, deletion of data representing certain facts necessitates deletion of data representing completely different facts
==Denormalization==
