Normalisation

• Computing
• Further Education (Key Stage 5)

Normalisation

Normalisation

Normalisation

Normalization is the process of organizing the attributes and tables of a relational database to minimize redundancy and dependency. 

It involves dividing large tables into smaller tables and defining relationships between them.

There are several levels, which we call, "normal forms", each building upon the last, that are used to guide the normalization process.

Primary keys

1. Must be unique within the table, but it can be made of multiple attributes.
2. Must be a single attribute and cannot contain null values.
3. Uniquely identifies a record within a table and can be duplicated in other tables.
4. Is optional and not required for relational databases.

Composite keys

1. Made up of multiple attributes, each of those must be unique in the table.
2. Always optional & not commonly used in relational databases.
3. Consist of a single attribute that uniquely identifies each record within the table.
4. Cannot be used as foreign keys in other tables.

Field name

1. A vertical arrangement of data in a database.
2. Location I put in the sat nav to find my pigs.
3. A record of data arranged into fields or columns.
4. A label, assigned to a data attribute in a table.

Redundancy

1. Inefficient for data storage, retrieval and maintainance.
2. Unneccesary duplication or repitition of data in a database.
3. Efficient for data storage, retrieval and maintainance.
4. Neccesary duplication or repitition of data in a database.

First Normal Form (1NF)

• All field names must be unique.
• Values in fields should be from the same domain or data type.
• Values in fields should be atomic.
• No two records can be identical.
• Each table needs a primary key.

Normalise the table provided to 1NF

Second Normal Form (2NF)

• Must already be in 1NF.
• Every non-key column should be dependent on the whole primary key, not just part of it.
• Many to many relationships should be repaired. We can use a linking table to do this easily with the table's primary keys.

Normalise your table to 2NF

Third Normal Form (3NF)

• Must already be in 2NF.
• No transitive dependencies should exist.

That means If any field doesn't rely on the primary key, it shouldn't be there

Normalise your table to 3NF

DIY

Table for a sales company selling something of your choice

1: Put all the data which you think you'll need in one table.

2: 1NF

3: 2NF

4: 3NF