8.1 Database concepts

8.1 Database Concepts

A Database is a structured collection of items of data that can be accessed by different applications programs.

Why not use file-base system?

• Data Redundancy (Duplication)

• Data Inconsistency

• Lack of Data Integration (no connections)

• Limited Data Access (format)

• Difficulty in Managing Security

Multiple Choice

Is a file-based system a good method for storing organizational data?

• Yes

• No

• Efficient storage: Data is stored only once, minimizing redundancy.

• Consistency: Changes in one application are reflected across others, ensuring data consistency.

• Data independence: Queries are not affected by the data structure or the software used.

Multiple Choice

What is the best method for storing data in a computer system?

• File-based system

• Database

• Write it by hand on a piece of paper.

• Write the data in your hand.

Labelling

Label the different key words of a database.

Drag labels to their correct position on the image

record

field

table

Drag and Drop

A ​

Placeholder

is a group of similar data, in a ​

Placeholder

, with rows for each instance of an entity and columns for each attribute. A ​

Placeholder

is a row in a table in a database. A ​

Placeholder

is a column in a table in a database.

Drag these tiles and drop them in the correct blank above

table

database

record

field

​A	A PROFESSIONAL says​
​Table	Entity​
​Record	Tuple​
​Field	​Attribute

• ​Data is shared between applications using a database.

• To ensure data consistency and integrity the updating is control using transactions and also it is automatically updating using the pointers.

• Pointers (keys) between tables minimize data duplication and establish relationships between them.

​Relationships can take several forms:

» one-to-one, 1:1

» one-to-many, 1:m

» many-to-one, m:1

» many-to-many, m:m.

8.1.4 Entity-relationship (E-R) diagrams

Labelling

Label.

Drag labels to their correct position on the image

one (and only one)

zero or one

one or many

one

zero or many

many

8.1.5 The normalisation process

​Normalisation is used to construct a relational database that has integrity and in which data redundancy is reduced.

8.1.5 The normalisation process

Example of bad practice:

8.1.5 The normalisation process

First normal form (1NF) - entities do not contain repeated groups of attributes.

8.1.5 The normalisation process

First normal form (1NF) - entities do not contain repeated groups of attributes.

8.1.5 The normalisation process

Second normal form (2NF) – entities are in 1NF and any non-key attributes depend upon the primary key. There are no partial dependencies.

8.1.5 The normalisation process

Third normal form (3NF) – entities are in 2NF and all non-key attributes are independent. The table contains no non-key dependencies.

8.1.5 The normalisation process

Third normal form (3NF)