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Essay Unit 18 - Database Design Assignment 1
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Essay Unit 18 - Database Design , Full Assignment 1, P1, M1 D1, Grade Distinction.
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Siratt Arif 1262443Unit 18 Assignment 1 – Features of a Relational Database
Explain all the following:
Entities
Entities are all the things and
items that are collected in a
database table, they are the
information recorded and can be
classified as objects and
properties.
Fields
Fields in relational databases are areas
where a unit of data is stored such as
properties, objects and entities. This is
the actual location of the data where
information is displayed in the
relational database. Fields have
properties as they define a specific cell
placed on any row whereas attributes
describe entities in terms of their
design.
Key Fields Eg primary and foreign keys
An example of key fields in relational database can be primary
keys, these are the items that have a unique field property
that is not repeated again within the table. There are a few
conditions that have to be true in order for a primary key to be
identified as a primary key, one of them is that the columns
must be distinctive, additionally there can’t be any blank
columns otherwise it will not meet the criteria needed to be
classified as a primary key. On the other hand, foreign keys are
a set of columns placed in a different table but that are at the
same time related to a primary key in a first table.
, Siratt Arif 1262443
How auto incremented keys work
Auto increment keys are used in databases in
order to generate numeric sequences for
purposes such as a new order number or
registering a new employee in the database.
Without using auto incremented keys
organisations and businesses would have
discrepancies in their databases and this would
cause chaos as a same number could be
assigned to employees with the same name or
with the same date of birth. The database can
recognise the last number registered so that it
is able to assign the next highest number for a
new order or for the registration of a new
employee automatically.
Different types of relationships with supporting diagrams
There are three types of relationships that can be applied between tables in a database:
One to one
This is the first type of relationship that can be applied to tables, as the name
suggests it means that a single item or record from a first table will only be
connected and therefore related to another singular item in the second table, this
creates a one to one relationships. In the same way even the single record in the
second table will only be connected to the single item in the first table.
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