Question

Question 5 (20 marks) a) Identify and briefly explain the three data anomalies found in a database design. (9 marks) b) What is normalisation? Name the three normal forms and their intended use. (9 marks) c) In resolving data anomalies, what exactly has normalisation achieve in a database design? (2 marks)

Answer 1

a)

Anomalies:

Anomalies are the problem which arises due to data insertion, data update or data deletion. This problem arises in a database that is unnormalized.

Modification/Update anomalies:

Update anomaly is data inconsistency after the update operation occurs. It arises due to partial updates and redundancy. In a partial update, some record is updated but some record is not updated or changes being made incorrectly.

Insertion anomalies:

When we can't insert a record into the database without the presence of some other attribute, then insertion anomalies occur.

Deletion anomalies:

When we delete a record from the database that has some attribute that should not be deleted, then deletion anomalies occur.  

For example:

We are deleting a student record and he is the single student who is enrolled in an extra course but the extra course is also deleted with the student.

b)

Normalization:

Normalization is used to avoid anomalies.

First Normal Form:

A table is said to be in first normal form if and only if each cell of the table contains the atomic value. By default, every relation is in the first normal.

Second Normal Form:

If there is no partial dependency then the relation is said to be in first normal form.

A functional dependency A->B is a partial dependency if some attribute 'X' belongs to A, can be removed from X and then dependency still holds.

Third Normal Form:

A relation or table is in third normal form if there is no transitive dependency.

c)

Anomalies are the problem which arises due to data insertion, data update, or data deletion.

Normalization is used to avoid anomalies.

In normalization, we break one table into multiple tables to remove the anomalies. The anomalies arise in a database that is unnormalized.

Answer 2

Bro is this your Database management assignment from deakin?