mysql-(iii)-The three paradigms of database design

I. The location of the database design in the business process

To abstract the original requirements into a business model when required analysis

Written requirement Specification < requirement Specification >

Overview design

Extract entities: Entity model, business model (Java Class)

Database design:

Data model, business model/entity model

Detailed design

...

Two. Three main paradigms of database design

First paradigm: Requires that each field of a table must be an indivisible independent unit

Counter Example

such as: Student  
The name has a name that was used and now

Student name    Xiao Wang |

Inquiry inconvenience         = = Illegal first paradigm

Student name Old_name   = = = In accordance with the first paradigm

Second paradigm: On the basis of the first paradigm, each table is required to express only one meaning. Each field in the table has a dependency on the primary key

Counter Example

Employee (Employee): Worker number   employee name   Department name  order name-violation of second normal form

Order name to design an order form to conform to the second paradigm

The third paradigm: on the basis of the second paradigm, it is required that only the primary key can directly determine the dependencies of each table except the primary key.

Employee Table: Employee number (primary key)  employee name   Department number      ...

The department name is related to the department number, and it is related to the employee number.

The solution is to create two tables, plus external constraints.

mysql-(iii)-The three paradigms of database design