Interview Q&A / SQL & DBMS

1. What is normalization? Explain 1NF, 2NF and 3NF.

   Normalization organises tables so each fact is stored once. 1NF means single values per cell, 2NF removes columns that depend on only part of a composite key, and 3NF removes columns that depend on other non-key columns.

   IntermediateIn-depth2 min read
2. What is a partial dependency and how does 2NF remove it?

   A partial dependency is when a non-key column depends on only part of a composite primary key. 2NF requires 1NF plus no partial dependencies, which you achieve by moving that column to a table keyed by that part.

   IntermediateQuick answer1 min read
3. What is denormalization and when would you use it?

   Denormalization deliberately adds redundant data, such as copied columns or precomputed totals, to avoid joins and speed up reads. It trades storage and write complexity for read performance, and suits read-heavy reporting.

   IntermediateQuick answer1 min read