What is an entity-relationship diagram (ERD)?

Short answer: An Entity-Relationship Diagram (ERD) is a graphical representation of entities and their relationships to each other within a database.

Explain a bit more

It is used to visualize the structure of a database and how tables (entities) relate to one another. Entities are represented as rectangles. Attributes are shown as ovals connected to their entities. Relationships are represented as diamonds, showing how entities interact. ERDs help in the conceptual design phase of a database, outlining entities, relationships, and keys before implementation.

Real-world example (ShopNest)

ShopNest’s SQL Server database stores customers, products, and orders. Good indexes and clear foreign keys keep checkout queries fast and safe.

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.