What do 1NF, 2NF and 3NF mean in plain language?

Options

1. 1NF: atomic values. 2NF: whole key. 3NF: only the key (Correct option)
2. They are three different types of index that speed up queries
3. They are three isolation levels that control the transactions
4. They are three types of backup that protect the database

Answer

1NF: each cell has one atomic value and no repeating groups. 2NF: every non-key column depends on the whole primary key. 3NF: non-key columns depend only on the key, not on other non-key columns

Why

Normalization organizes tables to avoid duplicated data and update bugs.

• 1NF: one value per cell (no lists like "red,blue" in a column) and no repeated column groups.
• 2NF: (with a composite key) every other column must depend on the entire key, not just part of it.
• 3NF: columns must depend on the key and nothing else. Example: orders(order_id, customer_id, customer_city): city depends on the customer, not the order, so move it to customers.

Memory trick: "the key, the whole key, and nothing but the key".

Remember

Data depends on the key, the whole key, and nothing but the key.

Key terms

• Normalization
• Normal forms (1NF, 2NF, 3NF)
• Junction table
• Foreign key
• Schema
• Table