First, Second & Third Normal Form

Question 1

What is normalisation?

Answer 1

Data is normalised in order to reduce redundancy and inconsistency and to make it easier to use.

Question 2

What is a table in before it gets to first normal form?

Answer 2

Unnormalised form. 0NF.

Question 3

How do you recognise 1NF?

Answer 3

A table is in 1NF if every data value in a field is atomic and each record does not contain repeating data.

Question 4

What is atomic data?

Answer 4

It means the data value cannot be broken down any further.

Question 5

Is student name an example of atomic data?

Answer 5

No, because it can be split into ‘forename’ and ‘surname’.

Question 6

How do you show a primary key?

Answer 6

With a . (Student No)

Question 7

What are the checks for 1NF?

Answer 7

Does the table have a primary key? Is each field name unique? Are there any repeating fields in a single record? Is all the data within a field atomic?

Question 8

How do you recognise 2NF?

Answer 8

A table is in 2NF if it is 1NF and all its non-key attributes are dependent on the entire primary key (or there are no partial key dependencies).

Question 9

2NF is based on f_________ d_________.

Answer 9

Functional dependance.

Question 10

Checks for 2NF?

Answer 10

Is the table in 1NF? Can all of the non-key fields be found out by using the entire primary key?

Question 11

How do you recognise 3NF?

Answer 11

A table is in 3NF if it is in 2NF and there is no functional dependency between non-key items. ‘Are any of the non-key fields dependent on any other non-key fields? If the answer is ‘No’, then the table is in 3NF. The rule here is that a new table needs to be created for each new dependency.

Question 12

Checks for 3NF:

Answer 12

Is the table in 2NF? Are all non-key attributes fully dependent on the primary key?

Question 13

Describe the correct notation for table structures.

Answer 13

The table name should be in capitals. The attributes (field names) in brackets separated by a comma. The primary key is underlined and foreign keys are over lined.

Question 14

What are the advantages of normalisation?

Answer 14

Removes redundancy, increases consistency, increases integrity, easier maintenance, flexibility for future expansion.

Question 15

What are the disadvantages of normalisation?

Answer 15

Increased CPU storage, longer to process. They’re not always necessary.