Question

******Please don't use handwriting and i need unique answer ... Thank you

Q3:

Consider the following relation:

Student-Dept = (Student-ID, Course, SportActivity, Dept-Name, Building)

Having following multivalued dependencies:

            F ={ Student-ID ®® Course

                   Student-ID ®® SportsActivity               

      Dept-Name ®® Building }

Explain in your own words why the Student-Dept relation is not in 4NF. Then, convert the Student-Dept relation in 4NF. Also, provide the justification for each step you perform during normalization (4NF). Note: The SportActivity here means any sport a student is participating in. For example, a student with ID = 123 can participate in soccer and badminton.

Q4:

In your own word, explain why do designers use Denormalization? What is the limitation of using Denormalization? Name and explain a better alternative approach than Denormalization.

Answer 1

Q3) For 4NF following should be true.

1. It should be in the Boyce-Codd Normal Form (BCNF).
2. the table should not have any Multi-valued Dependency

• For a dependency A → B, if for a single value of A, multiple values of B exists, then the relation will be a multi-valued dependency.

and for Student-Dept = (Student-ID, Course, SportActivity, Dept-Name, Building) rule 2 is not being fullfilled. so inorder to convert it into 4NF we will just divide the tables.

(Student-ID, Course) , ((Student-ID,SportActivity ) (Student-ID,Dept-Name) (Dept-Name, Building)

Now our tables are in 4NF.

Q4) Denormalization is used in a relational deatabase and is a method to increase the performance of read-oriented data retrival. Designers use Denormalization method as an optimization technique in making sense of redundant features and avoiding the use of expensive traints. It helps in improving the performance of the overall service.

Denormalization increases table count and in some cases complexity. If an aplication keeps changing then denormalization needs to be eveluated everytime it changes.