What is normalization and denormalization?

Purpose:

• This question tests whether a candidate has a theoretical understanding of how storage technologies have evolved and whether they have made an attempt to understand proper database design.
• A lack of being to awareness of these concepts may indicate ignorance of lack of industry experience.

Potential Answer:
Normalization is where we try to eliminate duplication of data, and dependency. Denormalization is just the opposite usually done for performance improvements to avoid unnecessary joins.

You can start talking about the different levels of normalization but this may bore your interviewer. Rather just allude to the fact that there are different levels and that the best practice is 3NF. Also perhaps juxtapose this with the NoSQL and BigData movements where data duplication is not as frowned upon as in the relational world.