■ DBMS Short Answer Notes (Units 1–3)

■ UNIT 1 – Introduction to DBMS

1. What is DBMS?

DBMS (Database Management System) ek software hai jo data ko store, manage aur access karne me madad karta hai. Example – MySQL, Oracle.

Data – raw facts and figures. Information – processed form of data jo useful ho.

DBMS me data redundancy kam hoti hai aur data security zyada hoti hai. File system me duplication hoti hai.

Data Independence ka matlab hai ek level ke change ka dusre level par effect na hona.

DBA (Database Administrator) wo person hota hai jo database manage karta hai – user access, backup aur recovery ka kaam karta hai.

Key ek attribute ya attribute ka group hota hai jo record ko uniquely identify karta hai. Example – Roll No.

Primary Key, Foreign Key, Candidate Key, Super Key – sab alag purpose ke liye use hoti hain.

Jab ek attribute ka value dusre attribute par depend kare to use functional dependency kehte hain.

Normalization ek process hai jisse data redundancy kam hoti hai aur data accuracy badhti hai.

1NF – Repeating groups remove karo. 2NF – Partial dependency hatana. 3NF – Transitive dependency hatana.

SQL ek standard language hai jo database me data create, insert, update aur retrieve karne ke liye use hoti hai.

DDL (CREATE, ALTER, DROP) – structure change karne ke liye. DML (INSERT, UPDATE, DELETE) – data manipulate karne ke liye.

SELECT ka use data retrieve karne ke liye hota hai. Example: SELECT * FROM Students;

JOIN ka use do ya zyada tables ke data ko combine karne ke liye hota hai. Example: INNER JOIN, LEFT JOIN.

SUM, AVG, COUNT, MAX, MIN – ye functions calculations ke liye use hote hain.

■ Quick Tip: Exam ke time short definitions aur SQL syntax yaad rakhna sabse zyada helpful hota hai!