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Chapter I Overview of databases

Ah Wen (Alvin)

1.1. Introduction

1.2. To put it simply. Database (database) is a warehouse for storing data, so in order to store and manage the data conveniently, it stores the data on disk according to specific rules. Through the database management system, it can effectively manage the data stored in the database.

1.2. Database paradigm

Database generics are the rules that the database should follow. Database generics are also called paradigms. At present, the four most commonly used paradigms in relational databases are:

The first normal form (1NF)

Second normal form (2NF)

The third normal form (3NF)

Fourth Paradigm (BCNF)

So here's a brief introduction. The content of the first paradigm

When designing a database, the minimum normal form that the database needs to meet is the first normal form, the first normal form.

There can be no duplicate fields in the table

Each field cannot be split

A database, then if even the first paradigm can not be satisfied. That would be unqualified. Only when the first paradigm is satisfied, it is further refined and subdivided according to the specific business.

1.3.The SQL language

The database management system manages the database in the database through SQL language. SQL is a query and design language. It is mainly used to store data, query data, update data and manage relational database.

SQL language is divided into three parts.

DDL (Data Definition Language) statements that define database tables, view indexes, triggers, and so on.

Create

Alter

Drop

Rename

Truncate

Comment

DML (Data Manipulation Language) statements are used to insert data, query data updates, and delete

Select

Insert

Update

Delete

DCL (Data Control Language) statement, which is used to control the user's access

Grant

Revoke

1.4. Common data systems

1. Oracle Oracle

2. DB2 of IBM

3 、 Sybase

4. Microsoft Access and SQL Server

6. Open source PostgreSQL

7. Open source MySQL

1.5.Introduction of Mysql database

MySQL is a relational database management system developed by MySQL AB Company of Sweden and currently belongs to Oracle Company. MySQL is an associated database management system that stores data in different tables instead of all data in a large warehouse, which increases speed and flexibility.

MySQL is an open source small relational database management system developed by the Swedish company MySQL AB. MySQL is widely used in small and medium-sized websites on Internet. Because of its small size, high speed and low total cost of ownership, especially open source, many small and medium-sized websites choose MySQL as the website database in order to reduce the total cost of ownership.

Mysql features:

Support multiple operating systems: AIX, FreeBSD, HP-UX, Linux, Mac OS, NovellNetware, OpenBSD, OS/2 Wrap, Solaris, Windows, etc.

2 support multithreading and make full use of CPU resources.

3. Large databases are supported. It can handle large databases with tens of millions of records.

4. Multiple storage engines are supported.

Version

Alpha development version.

Beat test version.

The Beat version of Gama has been released for some time.

Generally Available (GA) stable version.

1.6. How to learn the database

Learning database is mainly a lot of practice. The summary is as follows:

Practice of getting on the computer more

Write more SQL statements

Review more theoretical knowledge

1.7. Activity topics in this chapter

(1) A brief description of the database paradigm

(2) what are the SQL languages?

(3) what are the common database systems?

(4) briefly describe the features and version of Mysql.

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