Database-Normalisation

Normalisation is:

• Removing all necessary data from a database

• Organising a database to remove repeated entries and increase the accuracy of the data

• Putting fields from different tables into one big database

Which of the following statements fully describes data in 2NF:

• When any repeating fields have been removed and the table is given a primary key

• When all repeating entries of data are removed and the fields in each table are directly related to the primary key and no fields are present that are not related to each other

• When all the fields in each table are directly related to the primary key

An advantage of normalisation is:

• The storage space needed for a normalised database is likely to be smaller

• The process of normalising a database is very easy and doesn’t require any skill

• It is possible to see previous details that have been changed, such as a customer’s address, as we can look back at an older entry

A disadvantage of normalisation is:

• The data loses its integrity as some of it is removed in the normalisation process

• The process of searching the database may be slower due to a higher demand on the central processing unit (CPU)

• Removing redundant data means that links cannot be created between tables

What is an atomic field?

• A field that contains multiple items of data

• A field that is repeated

• A field that contains only one item of data

What is a foreign key?

• A unique identifier in a database

• A primary key of one table that appears in another table

• A field that should not be in a table and needs removing

A relation is in 1NF if it doesn't contain any ____________?

• Determinants

• Repeating groups

• Null values in primary key fields

• Functional dependencies

A table is in 2NF if the table is in 1NF and what other condition is met?

• There are no functional dependencies.

• There are no null values in primary key fields.

• There are no repeating groups.

• There are no attributes that are not functionally dependent on the relation's primary key.

When you normalize a relation by breaking it into two smaller relations, what must you do to maintain data integrity?

• Remove any functional dependencies from both relations

• Assign both relations the same primary key field(s)

• Create a primary key(s) for the new relation

When designing a database you should ____.

• make sure entities are in normal form before table structures are created

• create table structures then normalize the database

• only normalize the database when performance problems occur

• consider more important issues such as performance before normalizing