What is Second Normal Form (2NF)?

A table is in Second Normal Form (2NF) when it is in 1NF AND every non-key attribute is fully functionally dependent on the entire primary key — no partial dependencies. This only applies to tables with composite primary keys. Example: a table (order_id, product_id, product_name, quantity) — product_name depends only on product_id (partial dependency), not the full composite key. Fix: split into order_items(order_id, product_id, quantity) and products(product_id, product_name). Tables with single-column primary keys are automatically in 2NF if they are in 1NF.