Reference article:
Database design paradigm 3
to sum up:
Paradigm 1: Column inseparable, atoms; for example: address information extraction provinces and cities.
The second paradigm: the non-primary key column is fully dependent on the primary key column, a table just to save a class of data; for example: student enrollment information, student number, course name, credits, you need to course information (course name, credits) extracted separately.
Paradigm 3: There is no transfer dependent, i.e. between the non-primary key column, there is no relationship to each other, non-primary key column is directly associated with a primary key column, rather than indirectly correlation between the non-primary key column.