Relational Algebra in DBMS 

 Relational Algebra kya hota hai?

Relational Algebra ek query language hai jo hum databases (tables) se data nikaalne ke liye use karte hain. Yeh batata hai ki kaunsa operation perform karna hai taaki required result mile.

Simple words mein: Relational Algebra ek tareeka hai tables pe operations perform karne ka – jaise filter karna, join karna, columns select karna, etc.

---

 Kya kaam aata hai Relational Algebra?

• -> SQL (Structured Query Language) ka base hai.

• -> Query ko mathematically samajhne mein madad karta hai.

• -> Query optimization mein bhi kaam aata hai.

• 
  

 Basic Concept – Table ya Relation

Relational Algebra mein table ko relation bola jata hai.

Example Table: Students

 Relational Algebra ke Operations

Do types ke operations hote hain:

1. Basic Operations (Set-based)

2. Special Relational Operations

1. Select (σ)

Yeh operation rows ko filter karta hai – jaise SQL ka WHERE.

 Example:

CSE department ke students chahiye:

 Output:

2. Project (π)

Yeh operation specific columns ko select karta hai – jaise SQL ka SELECT.

 Example:

Sirf students ke naam chahiye:

 Output:

3. Union (⋃)

Do tables ko combine karta hai – duplicate rows hata ke.

Example:

Students_CSE

Students_ECE

 Output:

4. Set Difference (−)

Pehle table mein jo rows hain lekin second table mein nahi, unko return karta hai.

 Output:

5. Cartesian Product (×)

Har row ko doosri table ki har row ke saath combine karta hai.

Example:

Students

Courses

 Output:

6. Rename (ρ)

Table ya column ka naam change karne ke liye use hota hai.

 Join Operations – Tables ko merge karne ke liye

Natural Join (⨝)

Common column ke basis par rows ko join karta hai.

Example:

Students(RollNo, Name, Dept)
Departments(Dept, HOD)

 Output:

---

 Quick Summary Table

---

 Conclusion

• -> Relational Algebra ek toolset hai jo batata hai ki database pe kaise kaam karna hai.

• -> Yeh SQL ke peechhe ki logic ko samajhne mein madad karta hai.

• -> Har serious DBMS learner ko yeh samajhna chahiye, especially agar aap query optimization ya DB theory mein interest rakhte ho.