Soft exam Summary (1) Database Design

Database Design is a must-have question. Of course, it is also essential for our development programs. Now we will summarize the database design. I. database design phase division first, let's take a picture to gain an intuitive understanding of the Database Design Process (1) Requirement Analysis objectives: through investigation and research, measure the test taker's understanding about user requirements and handling results:

Database Design is a must-have question. Of course, it is also essential for our development programs. Now we will summarize the database design. I. database design phase division first, let's take a picture to gain an intuitive understanding of the Database Design Process (1) Requirement Analysis objectives: through investigation and research, measure the test taker's understanding about user requirements and handling results:

Database Design is a must-have question. Of course, it is also essential for our development programs. Now we will summarize the database design.

I. database design phase division

First, let's take a look at the database design process.

(1) Demand Analysis

Objective: To understand user requirements and handling requirements through investigation and research

Result: sort out the requirement statement. The Basis and basis for future design. Including: data contained in the database, data features, usage frequency, and data

For example, the data name, type, data requirements, and the size of the data used are usually managed using a data dictionary.

(2) Conceptual Structure Design

Objective: to abstract the data and requirements of requirement analysis, construct the data that reflects the user environment, and create a conceptual model for data interconnectivity.

(3) Logical Structure Design

Objective: to convert a E-R diagram to a relational pattern based on relevant rules. Primary Key, foreign key, and constraint are determined based on the theory of normalization.

Result: The data definition language provided by DBMS is written as the data mode.

(4) Physical Design

Objective: to convert a logical model to a physical model, including the file structure and index design process

2. E-R Model

(1) types of entities, attributes, contacts, and contacts (numbers)

(2) design steps: first design a local E-R diagram, then merge (view integration ). Efforts should be made to eliminate inconsistencies between partial ergraphs during merge

Conflict types of local ergraphs during merge:

1) attribute conflict: Conflicts between attribute domains and attribute values

2) Name Conflict: disagree with the same name, and consent with different names

3) structure conflict: Different abstractions of the same object in different applications, and the number of attributes of the same object in a non-graph are not exactly the same


(3) Local E-R diagram design steps: to determine the scope of the local view (such as procurement-related), to identify each part of the entity and between entities

Contact feedback attributes of entities and links between entities

E-R graph to link mode conversion:

1) convert an object to a relational model

2) one-to-one connection is converted into an independent link mode-attribute: the connection itself and the code of the connected attribute and any one

Link modulo merge of end-to-end -- attribute: The Code of adding two links and the attribute of another link

3) one-to-many relationship. A relational model can be formed separately-the Code of each object and the attributes of the contact itself. Merge with n-end --

Add the code on the other end and the attributes of the contact.

4) Multi-to-Multi-contact. Only one independent link mode can be converted. The Code of each object connected to the contact and the attributes of the contact.

5) connect multiple entities. Similar to the first four