Module 03b - Normalization

Question 1

Insertion anomalies

Answer 1

we cannot add a new row to the database unless we add another independent data

Question 2

Update anomaly

Answer 2

If we change a row we have to make changes in more than one place or else the database will be inconsistent.

Question 3

Deletion anomaly

Answer 3

If one data is deleted from the database, we loose information that we had related to another data.

Question 4

Source of anomalies and solution

Answer 4

Question 5

Normal Forms

Answer 5

1NF - A table that qualifies as a relation AND has a defined primary key

2NF - all of its non-key attributes are dependent on all of the primary keys

3NF - It’s in 2NF and has no determinants except the primary key

BCNF - If every determinant is a candidate key

Question 6

Is higher level of NF always desired?

Answer 6

No. Depends on the application

Question 7

Procedure of normalize the tables

Answer 7

Question 8

Multivalued dependencies

Answer 8

Occurs when a determinant is metched with a particular set of values. The determinant of a multivalued dependency can never be a primary key

Question 9

MVD and 4NF

Answer 9

Multivalued dependencies are not a problem if they are in a separate relation, so: Always put multivalued dependencies into their on relation (4NF)

Question 10

4 Normal Form

Answer 10

Is a normal form used in database normalization. Introduced by Ronald Fagin in 1977.

For every one of its non-trivial multivalued dependencies, X–>–>Y, X is a superkey

Question 11

Superkey

Answer 11

a set of attributes of a relation variable for which it holds that in all relations assigned to that variable, there are two distinct tuples (rows) that have the same values for the attributes in this set.