Database normalization


A particular database is normalized to satisfy a particular level of normalization (either 1NF or 2NF or 3NF). One of the tables contains, among other fields, a column for the City and a column for the Zip Code. Assuming that there is a many-to-one mapping between the set of Zip Code(s) and City, we may conclude that the database is definitely NOT in xNF form. What is the integer x (1, 2, or 3)?


There is many- to - one mapping between column city and zip code which states that every non-key attributes should be dependent on the primary key but here table is in 2-NF not in 3-NF because all non key attributes are fully functional dependent on the primary key
As we know that a relation can’t be in 3-NF if non-prime attributes depends on another non-prime attributes(i.e. they are transitively dependent on candidate key )
since multiple zip code can give same city so it is a non-prime attributes similarly a city can give multiple zip code and hence city is also non-prime attributes since there is dependency between non-prime attributes to non-prime attributes (city->zip code) so not in 3-NF Normalisation form