What is referential integrity in relational databases?

Short answer: Referential integrity ensures that relationships between tables remain consistent. Specifically, it guarantees that foreign keys in a table must match primary keys in another table, or they must be NULL.

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.