I don't consider this a good example of wanting 3NF.<p>> A hypothetical example of a failure to meet third normal form would be a hospital database having a table of patients which included a column for the telephone number of their doctor. The phone number is dependent on the doctor, rather than the patient, thus would be better stored in a table of doctors. The negative outcome of such a design is that a doctor's number will be duplicated in the database if they have multiple patients, thus increasing both the chance of input error and the cost and risk of updating that number should it change (compared to a third normal form-compliant data model that only stores a doctor's number once on a doctor table).<p>For instance having a single doctor row means that input from all a doctors patients overwrite each other's info about the doctor. Some may have special/private numbers or an incorrect one overwriting good data. This form only makes sense if doctors also use the system to provide their own canonical data.