IT - Unit 5

Lesson 1

Key Terms:

Field - An individual data item within a record. Should only contain one piece of data.

Foreign Key - Data types of these fields must be the same. This is a field that is a primary key in another table.

Primary Key - This is a field in a table that allows each record to be uniquely identified.

Table - A data structure made up of from rows and columns that contain data. The data this contain can be about anything. 

Record - It is the collection of data about a single item. It is made up of fields.

Relationship - Two fields in different tables depend on one another.

Data Type - The format of the data that is entered into a field.

Secondary Key - Can be used to sort the data into a different order than the primary key. Any field could be one of these.

Lesson 2

Entities:

An entity is a person, place, thing or concept about which data can be collected. An entity is not individual pieces of data, that is a field or attribute. Entities can be linked together in a database using a relationship.

Relationships:

Entities can be linked together, this link is called a relationship, there are 3 types of relationship between entities. One-to-One, One-to-Many, Many-to-Many.

One-to-One: This exists when the primary record will have only one related record. This can normally be resolved by putting these in the same table.

One-to-Many: This is the most common type of relationship between entities. Where a single instance of an entity is associated with many instances of another entity.

Many-to-Many: Many instances of…