What is the difference between 1NF and 2NF?

Short answer: 1NF (First Normal Form): Ensures that the table has atomic columns (no multi-valued or repeating groups) and each row has a unique identifier (Primary Key). 2NF (Second Normal Form): The table must be in 1NF and all non-key columns must depend on the entire primary key (i.e., there should be no partial dependencies).

Example code

A table with a composite primary key (e.g., StudentID, CourseID) where non-key attributes like CourseName only depend on CourseID would violate 2NF because CourseName is partially dependent on the composite key. You would separate this into two tables (one for Courses and one for Students).

Real-world example (ShopNest)

Product and Category are separate tables (normalized). The order line stores product id + price snapshot—not a giant duplicated product blob.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.