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What are the paradigms of relational databases? Many novices are not very clear about this. In order to help you solve this problem, the following editor will explain it in detail. People with this need can come and learn. I hope you can gain something.

Normalization is a detailed process after the initial work of identifying data elements, relationships in the database, and defining the required tables and items in each table. Design paradigm (paradigm, database design paradigm, database design paradigm) is a collection of relational patterns that conform to a certain level. The construction of the database must follow certain rules. In a relational database, this rule is the paradigm. Relationships in relational databases must meet certain requirements, that is, different paradigms.

There are six paradigms for relational databases:

The first paradigm (1NF), the second paradigm (2NF), the third paradigm (3NF), the Badesco paradigm (BCNF), the fourth paradigm (4NF) and the fifth paradigm (5NF).

The paradigm that meets the minimum requirements is the first normal form (1NF). The 2NF that meets more requirements on the basis of the first paradigm is called the second paradigm, and so on. Generally speaking, the database only needs to satisfy the third normal form (3NF).

When designing a relational database, a reasonable relational database is designed in accordance with different specification requirements. These specifications are called paradigms. The higher the paradigm database, the lower the redundancy.

The first paradigm

Columns without duplicates

Each column of a database table is an indivisible atomic data item, not a collection, array, record, or other non-atomic data item. If an attribute in an entity has more than one value, it must be split into different attributes

In any relational database, the first normal form (1NF) is the basic requirement for the design of relational schema, and the general design must meet the first normal form (1NF). However, some relational models break through the limitation of 1NF, which is called non-1NF relational model.

In other words, whether or not the minimum requirements of 1NF must be met depends largely on the relational model used.

The second paradigm

Property is completely dependent on the primary key

The second normal form (2NF) is established on the basis of the first normal form (1NF), that is, to meet the second normal form (2NF) must first meet the first normal form (1NF).

A situation that does not conform to the second normal form occurs only when there are multiple primary keys. For example, if there are two primary keys, such an attribute cannot exist, and it depends only on one of the primary keys, which is not in line with the second normal form.

If there is a situation that does not conform to the second normal form, then this part of the attribute and the primary keyword should be separated to form a new entity, and there is an one-to-many relationship between the new entity and the original entity.

The third paradigm

Properties cannot be passed dependent on primary attributes (attributes do not depend on other non-primary key attributes)

The third normal form (3NF) is established on the basis of the second normal form (2NF), that is, to meet the third normal form (3NF) must first meet the second normal form (2NF).

If an attribute depends on other non-primary key attributes, while other non-primary key attributes depend on the primary key, then this property is indirectly dependent on the primary key, which is called transitive dependence on the primary attribute.

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