Types of Relationships

Types of Relationships

1. One to One

   • A one to one relationship is when one record is linked to another record in another table
   • inefficient and time consuming, may result in human errors
   • E.g. in a hospital patients information will be linked to one patients record.

2. One to Many

   • In a database one table will link to many tables
   • E.g. An ordering database one customer can link to many orders

3. Many to Many

   • Very hard to implement
   • More than one thing can be linked in one table to another
   • Usually people try to find a way to change many to many to one to many or one to one
   • E.g. Many videos to many customers

4. Information is stored in sets of related tables based on 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 (ERD) is a specialised graphic that shows the relationships between entities in a database