Basically, there are thee type of anomaly problem occurs in the relation tables:
1.Insertion anomaly
2. Deletion anomaly
3. updation anomaly
2. Deletion anomaly:
When we delete some data or record from the table and some other record is deleted by default then this is called as deletion anomaly.
Example:
let assume we have a table that contain the detail of student with their HOD detail.
If student left the college one by one and when the last student left the college then with the deletion of student record we also lose the HOD record because we store HOD detail with the student.