Normalization in plain English

Question

I understand the concept of database normalization, but always have a hard time explaining it in plain English - especially for a job interview. I have read the wikipedia p

Answer 1

Normalization is a set of rules that used to design tables that connected through relationships.

It helps in avoiding repetitive entries, reducing required storage space, preventing the need to restructure existing tables to accommodate new data, increasing speed of queries.

First Normal Form: Data should be broken up in the smallest units. Tables should not contain repetitive groups of columns. Each row is identified with one or more primary key. For example, There is a column named 'Name' in a 'Custom' table, it should be broken to 'First Name' and 'Last Name'. Also, 'Custom' should have a column named 'CustiomID' to identify a particular custom.

Second Normal Form: Each non-key column should be directly related to the entire primary key. For example, if a 'Custom' table has a column named 'City', the city should has a separate table with primary key and city name defined, in the 'Custom' table, replace the 'City' column with 'CityID' and make 'CityID' the foreign key in the tale.

Third normal form: Each non-key column should not depend on other non-key columns. For example, In an order table, the column 'Total' is dependent on 'Unit price' and 'quantity', so the 'Total' column should be removed.