Edgar F. Codd’s definition of First Normal Form (1NF) makes reference to the concept of ‘atomicity’. Codd states that the “values in the domains on which each relation is defined are required to be atomic with respect to the DBMS.”[5] Codd defines an atomic value as one that “cannot be decomposed into smaller pieces by the DBMS (excluding certain special functions)”

A Movie Database (Simplified)

To illustrate, suppose we have a table of movies. Notice that the Genres column may have many parts to it. This violates the

For a table to be in first normal form, every row-and-column intersection contains exactly one value from the applicable domain (and nothing else). In our table, Lord of the Rings has two elements in the Genres column. It has Adventure and Fantasy separated with a comma. It is good for us that the creators of the database have separated the items with a delimiter, such as a comma.

This series of posts discusses how to solve this problem programmatically, by example in SQL Server.