Redundancy means having multiple copies of the same data in the database. This problem arises when a database is not normalized. Therefore anomalies occur.
Options A, B, and C all three anomalies occur.
Now for an instance imagine course_name and course_instructor in this table has repetitions which can lead to problems. Problems caused due to redundancy are Insertion anomaly, Deletion anomaly, and Updation anomaly.
Insert Anomaly:
- If a student detail has to be inserted whose course is not being decided yet then insertion will not be possible till the time course is decided for the student. This problem happens when the insertion of a data record is not possible without adding some additional unrelated data to the record.
Delete Anomaly:
- If the details of students in this table are deleted then the details of course will also get deleted which should not occur by common sense.
- This anomaly happens when deletion of a data record results in losing some unrelated information that was stored as part of the record that was deleted from a table.
- It is not possible to delete some information without losing some other information in the table as well.
Update Anomaly:
- Suppose if the course name changes then changes will have to be all over the database which will be time-consuming and computationally costly.
- It will be in an inconsistent state if not the update is all over the database.
Q2 Anomalies
Which anomalies are present in the following table of a college?
|student_roll| |student_name| |course_name| |course_instructor|
This table has student_roll, course_name as the composite primary key.
Note: More than one option may be correct.
A. Insert anomaly
B. Update anomaly
C. Delete anomaly
D. No anomalies