Database three-paradigm non-repeating columns fully dependent primary key properties do not rely on non-primary properties

The three paradigms of database

2.1 First Normal (1NF) non-repeating columns

Each column of a database table in the first normal form (1NF) is an indivisible basic data item
Cannot have more than one value in the same column
That is, an attribute in an entity cannot have multiple values or cannot have duplicate properties.
In short, the first paradigm is a column with no duplicates.

In any relational database, the first paradigm (1NF) is the basic requirement for relational schemas, and a database that does not meet the first normal form (1NF) is not a relational database.

2.2 Second Normal form (2NF) property fully dependent on primary key [eliminate partial child function dependency]

Satisfying the second normal form (2NF) must first satisfy the first normal form (1NF).

The second normal form (2NF) requires that each instance or row in a database table must be divided by a unique region.

It is often necessary to add a column to the table to store the unique identity of each instance.
The second normal form (2NF) requires that the attributes of an entity depend entirely on the primary key. The so-called full dependency is the inability to have a property that depends only on the primary key, and if so, this part of the property and the primary key should be separated to form a new entity, and the new entity is a one-to-many relationship with the original entity. It is often necessary to add a column to the table to store the unique identity of each instance. In short, the second paradigm is that properties depend entirely on the primary key.

2.3 Third normal form (3NF) property does not depend on other non-primary properties [eliminate transitive dependencies]

Satisfying the third normal form (3NF) must first satisfy the second normal form (2NF).

In short, the third paradigm (3NF) requires that a database table not contain non-primary key information already contained in other tables.

For example, there is a departmental information table, where each department has a department number (dept_id), a department name, a department profile, and so on. Then the department number is listed in the Employee Information table, the department name, department profile and other departments related information can no longer be added to the Employee Information table. If there is no departmental information table, it should be built according to the third paradigm (3NF), otherwise there will be a lot of data redundancy. In short, the third paradigm is that properties do not depend on other non-principal properties.

Database three-paradigm non-repeating columns fully dependent primary key properties do not rely on non-primary properties