What are Relationships between Entities? – Database Management System (DBMS)

🧑‍🎓 What is Relationship?

A Relationship in DBMS defines how two or more entities are connected or associated with each other.

In other words, it shows how one entity is related to another in a real-world context.

🧑‍🎓 Example (Real-life):

In a university database:

👤 Student
📚 Course
The relationship could be:
👉 A Student ENROLLS in a Course

Here:

Student and Course are entities
ENROLLS is the relationship between them

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  <h2>🔢 Types of Relationships (Cardinality)</h2>
  <p class="subtitle">The lines don't lie. Switch cardinality and watch how many connections each side actually gets.</p>

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    <span class="m-type">1:1 (One to One)</span>
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  <p class="takeaway"><strong>The pattern is the definition.</strong> Count how many lines leave one side — that number alone tells you whether it's 1:1, 1:N, or M:N.</p>

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🧾 Relationship Degree:

The degree of a relationship refers to the number of entity sets that participate in a relationship.

Degree	Meaning	Example
Unary	Relationship between same entity	Employee manages another Employee
Binary	Relationship between two entities	Student ENROLLS in Course
Ternary	Relationship between three entities	Doctor prescribes Medicine to Patient

🧠 Summary:

🔹 Concept	📖 Description
Entity	Real-world object (e.g., Student, Course)
Attribute	Property of an entity (e.g., Name, ID)
Relationship	Describes how entities are connected (e.g., ENROLLS)
ER Diagram	Uses diamonds to show relationships between rectangles