Types of relationships

Types of relationships

1. One to one

   • Examples
     • In a hospital, nurses/doctors have the access to patient records. Only one person will have these specific records.
   • A one to one relationship is one record in one table, linking to a single other record in another table.
   • inefficient and time consuming; may result in human errors

2. One to many

   • Examples
     • One customer could be linked to many orders.
   • One record in one table could have links to many other data representations.

3. Many to many

   • Very hard to impliment
     • This then means that it is broken down into smaller groups such as one to many.
   • Many different pieces of data can be linked to somewhere with just as many pieces of data.
   • Examples
     • Rental; videos, bikes, car etc.

4. Information is stored in sets of related tables based on the entities

5. Relationships built through shared common fields

6. Overcome the problems of storing everything in single tables

7. Entity Relationship Diagram

   • An entity relationship diagram is a specialised graphic that shows the relationships between entities and a database
   • ERD