Database overview and common database introduction

foreword

This column will continue to update from the database concept to database SQL optimization (from the perspective of Java development, not from the perspective of a database administrator (DBA)). This is the first "Common Database Concepts" to open my database The trip mainly talks about the MySQL 8.0 database, which is also one of my commonly used databases. I hope to keep learning with you. For details on database download and installation, see: http://t.csdn.cn/H1vjv

1. Database overview

1. Reasons for database usage

Persistence:
saving data to a power-downable storage device for later use . In enterprise-level applications, data persistence means saving the data in memory to the hard disk for "solidification" , and the implementation process of persistence is mostly completed through various relational databases
. The main function of persistence: the data in memory Stored in a relational database , can also be stored in disk files, XML data files

2. The reason for choosing the database

• Open source code, low cost of use
• Excellent performance and stable service
• The software is small in size, easy to use, and easy to maintain
• With a long history, community users are very active, you can ask for help if you encounter problems
• time-tested

2. Database and database management system

1. Related concepts of database

1.1. DB: Database

The "warehouse" for storing data is essentially a file system that stores a series of organized data

1.2, DBMS: Database Management System (Database Management System)

A large-scale software for manipulating and managing databases, used to establish, use and maintain databases, and to manage and control data in a unified manner. Users access the data in the tables in the database through the database management system

1.3. SQL: Structured Query Language

A language specifically designed to communicate with databases

2. The relationship between database and database management system

A database management system (DBMS) can manage multiple databases, and developers generally create a database for each application. In order to save the data of the entities in the application, multiple tables are generally created in the database to save the data of the entity users in the program.
The relationship between the database management system, the database and the tables is shown in the figure

3. Common databases

1. Ranking of common database management systems

Currently common database management software includes Oracle, MySQL, MS SQL Server, DB2, PostgreSQL, Access, Sybase, and Informix. The following is the statistical result of DB-Engines Ranking's survey on the popularity of each database, check the latest database ranking: https://db-engines.com/en/ranking

Corresponding line chart: https://db-engines .com/en/ranking_trend

2. Common database introduction

2.1、Oracle

• In 1979, Oracle2 was born, it is the first commercial RDBMS (relational database management system). With the growing popularity of Oracle software, the company changed its name to Oracle Corporation
• In 2007, a total of 8.5 billion US dollars was enough for BEA Systems
• In 2009, SUM was acquired for a total of 7.4 billion US dollars. In 2008, SUN acquired MySQL for US$1 billion. It means that Oracle has the management right of MySQL at the same time, so far Oracle has become the absolute leader in the database field
• In 2013, Oracle surpassed IBM to become the second largest software company in the world after Microsoft
• Today, Oracle's annual revenue has reached 40 billion US dollars, which is enough to prove the value of commercial (fee) database software

2.2、SQL Server

SQL Server is a large commercial database developed by Microsoft, which was born in 1989. C#, .net and other languages ​​are often used, completely inherited from WinNT, and can also be well integrated with Microsoft BackOffice products

2.3、DB2

IBM's fee-based database products, often used in banking systems

2.4、PostgreSQL

PostgreSQL is extremely stable, most in line with SQL standards, open source, and has commercial-grade DBMS quality. PG processes text and SQL with a large amount of data faster.

2.5、SyBase

Has faded out of the historical stage, providing a very professional data modeling tool PowerDesigner

2.6、SQLite

Embedded small database, applied on the mobile phone. Zero configuration, SQLite3 does not need to be installed, configured, started, shut down or configure the database instance. When the system crashes, there is no need to do any recovery operations, and it will automatically recover when the database is used next time

2.7、informix

Produced by IBM, derived from the combination of Infomation and Unix, it is the first commercial database product to be ported to Linux. Only run on unix/linux platform, command line operation. High performance, supports clusters, and is suitable for systems with high security requirements, especially for banking and securities systems

3. MySQL introduction

• MySQL is an open source relational database management system , developed by Swedish MySQL AB (founder Micheal Windenius) in 1995, and quickly became the No.1 open source database
• In 2008, it was acquired by SUN (US$1 billion). In 2009, SUN was acquired by Oracle, and MariaDB came into being.
• After MySQL 6.x, it is divided into community edition and commercial edition
• MySQL is a relational database management system that keeps data in different tables instead of putting all the data in one big warehouse, which increases speed and improves flexibility
• MySQL can be customized, using the **GPL (GNU General Public License)** agreement, you can modify the source code to develop your own MySQL system
• MySQL supports large databases and can handle large databases with tens of millions of records
• MySQL supports large databases and data warehouses with 50 million records. The 32-bit system table file can support a maximum of 4GB , and the 64-bit system supports a maximum table file of 8TB.
• MySQL uses the standard SQL data language form
• MySQL can be allowed to run on multiple systems and supports multiple languages. These programming languages ​​include C, C++, Python, Java, Perl, PHP and Ruby, etc.

4.Oralce VS MySQL

Oracle: more suitable for large multinational companies because they are not sensitive to costs, but have higher requirements for performance and security
MySQL: due to small size, high speed, and low total cost of ownership , it can handle tens of millions of records Large-scale databases, especially the open source feature, have made many Internet companies and small and medium-sized websites choose MySQL as their website database.