Recognize databases and databases again

Recognize databases and databases again

I haven't summarized the database for a long time. Let's take a look.

What is the database used? Let's discuss it with us.

I. Introduction

Databases are developed from the file management system and are an advanced stage of data management. We all know that it is used to store data.

ToIt is an electronic file cabinet that allows you to add, delete, modify, and query data,However, it is not only used to store data. With the development of database technology

Exhibition, massive databases and large database systems have been widely used.

Layer 2 and Layer 3

The three layers are the physical data layer, the conceptual data layer, and the user data layer. Think about the three layers that are similar to what we are learning now.

1. Physical data layer: For more information about how to store raw data, see data access layer (D)

2. Logical Data Layer: for the overall logical description of all data in the database, see business logic layer (B)

3. User data layer: for data provided by some specific users, refer to the presentation layer (U)

For more information, see Layer 3. Layer 3 transfers data more through entities, so the Layer 3 of the database is interconnected.

Connected?

Ing

Data Consistency between Layer 3 databases is maintained through ing.

The ing between the user data layer and the logical data layer is generally defined in the user data layer.

The time ing between the physical data layer and the logical data layer is generally defined in the physical data layer.

Iii. Advantages

1. Data Sharing

The database contains information of all users. Users can also access the database through interfaces to share data, such as interconnection.

Data sharing in the Internet age, almost all information can be found on the Internet

2. Reduce data overhead

After data sharing is realized, users no longer need to create files separately, which reduces a large amount of duplicate data.

3. Centralized data control

Centralized control and management of data using databases, and the relationship between data through data model tables

4. Data Security, complete and Concurrent Control

Security: prevents data loss, error updates, and unauthorized use

Integrity: ensures data correctness, effectiveness, and compatibility.

Concurrency Control: Allows multiple users to access data at the same time, and prevents abnormal use between users.

5. fault recovery

The database management system can promptly discover and repair faults to prevent data from being damaged.

Summary:

The database has a lot of content and needs to be studied slowly. However, we can feel that the database is playing an increasingly important role now.

Learning is not a simple task. If we review it, we will have more resonance.