Relationship Pattern Design Theory

There are six database paradigms. The most common ones are the first and third paradigms. The higher the standard, the more redundant the paradigm data.

There are six database paradigms. The most common ones are the first and third paradigms. The higher the standard, the more redundant the paradigm data.

There are six database paradigms. The most common ones are the first and third paradigms. The higher the standard, the smaller the data redundancy.

First paradigm: (No score)

The basis of the paradigm. All paradigms must satisfy the first paradigm. Other paradigms are based on the first paradigm.

Second paradigm:

The first paradigm eliminates local dependencies and requires that the attributes of an object fully depend on the primary key.

If local dependency exists, you need to separate this attribute from the part of the candidate key to form a new entity.

Example

(Student ID, name, department, address, course, score );

Exist (student ID, course) --> (name, department, address, score );

It should be divided:

Student ID, course) --> (score)

(Student ID) --> (name, department, address)

Third paradigm:

Eliminate transmission dependencies based on the second paradigm.

Example

(Student ID) --> (name, department, address)

If the same Department address is the same, that is, the address depends on the department, the function dependency does not conform to the third paradigm.

It should be divided:

(Student ID) --> (name, Department)

(Department) --> (address)

After several paradigms are passed down, redundancy and exceptions will be eliminated, that is, the common problems of link pattern design will be eliminated ......