Recently , we talked about ERD Terminologies and discussed about entities and attributes in detailed. In case , you haven’t read the article it is a must read . Some wonderful details for you to go through.
It is time we discuss about how different entities in a design interacts together . Before we dive into it , you should know one very important thing about DBMS . When we design a DBMS , we are practically translating real life into it and perhaps this is why this field is one of the most practical in Computer Sciences. Due to this sole reason , designing a DBMS is just like your real world and how things ( objects ) interact out there is how they will interact here.
People interact with each other when they have a relationship/acquaintances between them . Our DBMS entities do the same . Two entities communicate with each other by a relationship
We will discuss about
- Degrees of Relationships
Behaviour or association between relation is called a relationship.This is represented by the following symbol
ERD Terminologies relationship is represented as below.
DEGREES OF RELATIONSHIPS :
Number of entities that share a relationship is called the degree of relationships . We have basically three type of degrees .
Unary Relationship :
When entity has a relationship with itself , that’s a unary relationship. Self-Joins are the perfect example. Usually when entity has a parent-child relationship in its columns , then this happens.
Example could be that you need to pass certain subjects to take others as they are pre-requisites of them . Presentation will be :
Binary Relationship :
When two entities share a relationship with each other that is a binary relationship . Example could be Teacher teaches a Subject. Two entities one relationship.
Ternary Relationship :
When three entities share a relationship with each other . Example could be a Students taking Subjects from Teachers.
Using the diagram of our ERD Terminologies . Here Student , Teacher and Subject has a ternary relationship.
You can see a design DBMS in making and we have created relationships among entities using relationships .
So far I have deliberately , kept you away from a lot of technical definitions . Remember the idea is to explain in human language and we have made great progress so far . In my next article , we will discuss the cardinality of entities with each other considering their relation and then we’ll move towards essence of DBMS. Stay Tuned!
Liked what you read? Share with your fellows students and subscribe to the email list to get all this in your e-mails.
Happy Learning !