What is normalization in SQL databases?

Without normalization, the same piece of information can end up duplicated across many rows — if a customer's address changes, you'd need to update it in every row that repeats it, and any row you miss creates inconsistent data.

Common normal forms

• 1NF (First Normal Form): each column holds a single, indivisible value — no repeating groups or lists inside a cell
• 2NF: builds on 1NF, removing data that only depends on part of a composite key
• 3NF: builds on 2NF, removing columns that depend on other non-key columns rather than directly on the primary key

The trade-off

Highly normalized databases reduce redundancy and keep data consistent, but often require more joins to reassemble related data for a query. Some systems intentionally "denormalize" parts of a database — reintroducing some redundancy — to improve read performance for specific, frequent queries.