Three paradigms of database

First normal form （ Make sure that each column remains atomic ）

Each column of the first normal form can no longer be split , It's called atomicity
The first paradigm is the most basic paradigm . All field values in the database table are indecomposable atomic values , That is, the database table meets the first normal form .

Second normal form （ Make sure that each column in the table is related to the primary key ）

On the premise of satisfying the first paradigm , Every field in the table is completely dependent on the primary key .
The second paradigm needs to ensure that every column in the database table is related to the primary key , You can't just relate to a part of the primary key （ Mainly for the union primary key ）.

Third normal form （ Make sure that each column is directly related to the primary key column , Not indirectly ）

• A table describes only one thing
• Each column in the table depends on the primary key
• Cancel the primary key transfer dependency in the second normal form

The third paradigm needs to ensure that each column of data in the data table is directly related to the primary key , Not indirectly .