Question 1

What is normalization in database design?

Accepted Answer

The process of organizing data to reduce redundancy and improve data integrity. Normalization organizes tables and columns to minimize redundancy. 1NF eliminates duplicate columns; 2NF removes partial dependencies; 3NF removes transitive dependencies.

Question 2

Which type of SQL JOIN returns only rows that have matching values in both tables?

Accepted Answer

INNER JOIN. INNER JOIN returns only the rows where the join condition is met in both tables. LEFT JOIN returns all rows from the left table; FULL OUTER JOIN returns all rows from both tables.

Question 3

What does ACID stand for in database transactions?

Accepted Answer

Atomicity, Consistency, Isolation, Durability — properties guaranteeing reliable transactions. Atomicity: all or nothing. Consistency: DB moves from one valid state to another. Isolation: concurrent transactions don't interfere. Durability: committed data survives crashes.

Question 4

What is the difference between DELETE and TRUNCATE in SQL?

Accepted Answer

DELETE removes specific rows and can be rolled back; TRUNCATE removes all rows and typically cannot be rolled back. DELETE is DML — it removes rows matching WHERE clause and logs each deletion (slower, rollback-able). TRUNCATE is DDL — it removes all rows at once (faster, usually not rollback-able).

Question 5

What is a SQL VIEW?

Accepted Answer

A virtual table based on the result of a SELECT query. A VIEW is a saved SELECT query that behaves like a virtual table. It simplifies complex queries, provides security by limiting visible columns, and does not store data itself.

DBMS & SQL — Fresher Interview Questions

More Fresher Topics

DBMS & SQL at Other Levels