Generalization, Specialization and Aggregation in DBMS 

 1. Generalization (Bottom-Up Approach)

 Kya hota hai?

Generalization ka matlab hota hai: do ya zyada similar entities ko combine karke ek general (common) entity banana.

Socho aap specific se general ki taraf ja rahe ho.

 Example:

Humare paas do entities hain:

• Car (wheels, engine)

• Bike (wheels, engine)

In dono mein common features hain, toh hum ek general entity bana sakte hain:

• Vehicle (common entity)

 Diagram:

 Vehicle ek common/general entity hai jo Car aur Bike dono ki common properties ko rakhta hai.

 2. Specialization (Top-Down Approach)

 Kya hota hai?

Specialization ka matlab hota hai: ek general entity ko uske specific types mein todna.

Socho aap general se specific ki taraf ja rahe ho.

 Example:

Ek entity hai:

• Employee

Ab hum Employee ko unki job ke basis par tod sakte hain:

• Manager

• Engineer

 Diagram:

 Yaha Employee ek general entity hai, jise hum uske specific roles mein divide kar rahe hain.

 3. Aggregation

 Kya hota hai?

Aggregation ka matlab hai: jab hum ek relationship ko bhi entity ki tarah treat karte hain.

Iska use tab hota hai jab ek relationship bhi kisi aur relationship mein participate karta hai.

 Example:

Maan lo:

• Professor teaches a Course → ye ek relationship hai.

• Ab hum chahte hain ki Classroom assign karein us teaching relationship ko.

Toh hum “Teaches” relationship ko entity maan lete hain, aur usse Classroom se connect karte hain.

 Diagram:

 Yaha Teaches relationship ko bhi entity ki tarah treat kiya gaya hai.

 Short Comparison Table

 Summary 

• Generalization = Similar cheezein → Combine karke ek general cheez banana

• Specialization = General cheez → Todna specific cheezon mein

• Aggregation = Jab ek relationship bhi kisi aur relationship mein use hota hai