Entities and Attributes in DBMS

 Entity kya hoti hai?

Entity ka matlab hota hai koi bhi real world cheez, person ya concept jiske baare mein hum data store karna chahte hain.

 Simple shabdon mein, Entity = Noun (Naam wali cheez)
Jaise:

• Student

• Teacher

• Car

• Book

• Course

Yeh sab cheezein alag-alag hoti hain aur inke baare mein hum database mein data store kar sakte hain.

 Example:

Agar hum ek college ka database bana rahe hain to:

• Student ek entity hoga

• Book bhi ek entity hoga

• Course bhi ek entity hoga

 Attribute kya hota hai?

Attribute ka matlab hota hai entity ke features ya characteristics — yani us entity ke baare mein information.

 Simple shabdon mein, Attribute = Adjective (Visheshan)
Jo entity ko describe karta hai.

 Example:

Agar Student entity hai, to uske attributes ho sakte hain:

• Student_ID

• Name

• Age

• Gender

• Course

 Example Table: Student Entity ke Attributes

• Entity: Student

• Attributes: Student_ID, Name, Age, Gender, Course

 Diagram – Entity aur Attributes

 Types of Entities

1. 1. Strong Entity

   • Apne aap exist kar sakta hai

   • Primary key hoti hai
      Example: Student, Employee

2. 2. Weak Entity

   • Kisi aur entity pe depend karta hai

   • Apna unique key nahi hota
      Example: Dependent (Employee ka baccha), Order_Item (Order ka part)

 Types of Attributes

 Real-Life Example – Library System

Agar aap ek library ka DBMS bana rahe ho:

• Entities:

  • Book

  • Member

  • Librarian

• Book ke Attributes:

  • Book_ID, Title, Author, Price

• Member ke Attributes:

  • Member_ID, Name, Contact, Email

 Summary Table