Chapter 6, Problem 10RQ

Explanation of Solution

Anomaly:

• Without normalization, redundancies occur in the table, and it may lead to errors or some sort of inconsistency. These are termed as anomalies.
• Anomalies occur when user wants to update the data in the table.
• There are three types of anomalies. They are,
  • Insertion anomaly
  • Deletion anomaly
  • Modification anomaly

Insertion anomaly:

• Certain attributes cannot be inserted in the database table without the presence of other attributes and causes the occurrence of insert anomaly.
• For example,
  • Suppose a student data need to be inserted in the STUDENT database table.
  • Student_name and dept are the combination of primary keys in the STUDENT relation.
  • The user must enter the values for both the keys. But, this is an anomaly here, because the user can enter only Student_name; the value for dept is unknown to the user until the student joins the department.

Deletion anomaly:

• Deletion of an attribute causes unintended loss of data or inconsistencies in the database and is referred to as deletion anomaly...