Relational Data Model in DBMS

Relational Data Model kya hota hai?

Relational Data Model ek aisa model hai jisme data tables ke form mein store hota hai. Har table ko relation kehte hain, aur ye table rows aur columns se banta hai.

Har row ko tuple (ya record) kehte hain.
Har column ko attribute (ya field) kehte hain.

Jaise aap Excel sheet dekhte ho — waise hi data tables ke form mein hota hai.

Basic Terms aur Unka Matlab

Term	Matlab (Meaning)
Relation	Table (rows aur columns ka group)
Tuple	Ek row ya record in table
Attribute	Column ya field in table
Domain	Possible values ka set kisi attribute ke liye
Degree	Kitne attributes (columns) hain ek table mein
Cardinality	Kitne tuples (rows) hain ek table mein

Example: Student Table

StudentID	Name	Age	Course
101	Ayesha	20	B.Tech
102	Rahul	21	BCA
103	Sneha	19	B.Sc

Table ka naam hai: Student
4 columns hain → StudentID, Name, Age, Course
3 rows hain → 3 students ka data
Age attribute ka domain ho sakta hai 16 se 60 years

Keys in Relational Model

Data ko uniquely identify karne ke liye keys use hoti hain:

1. Primary Key

Ek column ya columns ka group jo har row ko uniquely identify karta hai.
Example: StudentID yahan pe primary key hai.

2. Foreign Key

Ek table ka column jo dusre table ki primary key ko refer karta hai.
Isse tables ke beech relationship banta hai.

Tables ke Beech Relationship

Tables ko hum foreign key ke through connect karte hain — bina data repeat kiye.

Example: Student aur Course tables

Student Table

StudentID	Name
1	Riya
2	Aman

Course Table

CourseID	CourseName
101	DBMS
102	OS

Enrollment Table (link between student aur course)

StudentID	CourseID
1	101
2	101
2	102

Enrollment table mein StudentID aur CourseID dono foreign keys hain.
Isse pata chalta hai kaunsa student kaunsa course kar raha hai.

Features of Relational Data Model

Simple: Tables ko samajhna easy hota hai.
Flexible: Data ko modify karna aasan hota hai.
Secure: Data integrity maintain hoti hai.
Independent: Table ke structure change karne par queries ka effect kam hota hai.
SQL ka use hota hai data ko access aur manage karne ke liye.

Relational Model ke Fayde

-> Easy to understand
-> SQL ka use karke data access simple hota hai
-> Secure aur reliable
-> Redundancy kam hoti hai
-> Scalable (bade systems ke liye perfect)

Thode Disadvantages

-> Complex queries slow ho sakti hain
-> Bohot saare joins performance slow kar dete hain
-> Unstructured data (images, videos) ke liye best nahi hai

Summary

Relational Data Model ka main concept hai data ko tables ke form mein store karna aur keys se tables ko link karna. Ye model MySQL, Oracle, SQL Server, PostgreSQL jaise popular DBMS tools mein use hota hai.

The Hingineer