Data Gets Out of Sync

Why Normalization Exists Normalization exists to prevent a specific class of production failure: data that contradicts itself. When the same fact is stored in multiple rows or multiple tables, any update must touch every copy. Miss one, and your database has two different answers to the same question. This is not a theoretical concern. It is the number one source of 'the numbers do not match' bugs in real systems. Here is the canonical example: an employee table that looks reasonable until a department name changes. Alice and Bob say Engineering is on Floor 3. Carol says Floor 5. Which is correct? Nobody knows without checking a separate source. This happened because someone updated Carol's row but not Alice's and Bob's. The data contradicts itself. 3 The fix: store 'Engineering' and its l