Database Design Methodology

First, the database design method

1. Extract the entities from the project as required

2. Summarize the attributes of each entity

3. Determine the relationship between entities

Ii. three paradigms of database design

1, atomicity and database of each column is the smallest unit, according to the requirements of non-split

2. Each table describes only one entity, ensuring that each column in the database table is related to the primary key, not just one part of the primary key (primarily for federated primary keys)

3, each table should not contain redundant information, if the a table contains a table B's primary key, then a is not required to include the table B additional information

For example, the following table is an error demonstration:

Project number project name employee number name duty hour wage rate work place

Qixian, Kaifeng, Henan

The table contains engineering information, staff information, project hours information violates the second paradigm

The duty station can be divided into provincial and municipal counties violating the first paradigm

No project name, no engineering designation, illegal third paradigm

The table can be split into

1, the Project information table contains the project number project name

2. Employee Information sheet contains employee's name position

3. Project Work Hours table number of worker number

4. Job table duty hourly rate of pay

Database Design Methodology