数据库的分类有：
1.IBM DB2（是一个数据库管理系统，同时提供优化的性能，可用性，更高的生产力，并降低成本保 持安全性，完整性和用户数据的私密性。它的设计在Microsoft Windows，UNIX和Linux操作系统上运行）
2. Oracle Database（又名Oracle RDBMS，或简称Oracle。是甲骨文公司的一款关系数据库管理系统。它是在数据库领域一直处于领先地位的产品。可以说Oracle数据库系统是目前世界上流行的关系数据库管理系统，系统可移植性好、使用方便、功能强，适用于各类大、中、小微机环境。它是一种高效率的、可靠性好的、适应高吞吐量的数据库方案）
3.Informix（是IBM公司出品的关系数据库管理系统（RDBMS）家族。作为一个集成解决方案，它被定4.SQL Server（Microsoft SQL Server 是一个全面的数据库平台，使用集成的商业智能 (BI)工具提供了企业级的数据管理。Microsoft SQL Server 数据库引擎为关系型数据和结构化数据提供了更安全可靠的存储功能，使您可以构建和管理用于业务的高可用和高性能的数据应用程序）
5. MySQL数据库（MySQL是一个关系型数据库管理系统，由瑞典MySQL AB 公司开发，属于 Oracle 旗下产品。MySQL 是最流行的关系型数据库管理系统之一，在 WEB 应用方面，MySQL是最好的 RDBMS (Relational Database Management System，关系数据库管理系统) 应用软件之一）
6. PostgreSQL（PostgreSQL是一种特性非常齐全的自由软件的对象-关系型数据库管理系统（ORDBMS），是以加州大学计算机系开发的POSTGRES，4.2版本为基础的对象关系型数据库管理系统。POSTGRES的许多领先概念只是在比较迟的时候才出现在商业网站数据库中。PostgreSQL支持大部分的SQL标准并且提供了很多其他现代特性，如复杂查询、外键、触发器、视图、事务完整性、多版本并发控制等。同样，PostgreSQL也可以用许多方法扩展，例如通过增加新的数据类型、函数、操作符、聚集函数、索引方法、过程语言等）
7. Access数据库（Microsoft Office Access是由微软发布的关系数据库管理系统。它结合了 MicrosoftJet Database Engine 和 图形用户界面两项特点，是微软把数据库引擎的图形用户界面和软件开发工具结合在一起的一个数据库管理系统）

The classification of the database is:

  1. IBM DB2 (is a database management system, while providing optimized performance, availability, higher productivity, and reduce costs to maintain security, integrity and privacy of user data. It is designed in Microsoft Windows, UNIX and Linux Operating system)
  2. Oracle Database (also known as Oracle RDBMS, or Oracle for short. It is a relational database management system of Oracle. It has always been a leading product in the database field. It can be said that Oracle database system is currently the most popular relational database in the world. The management system has good portability, easy use, and strong functions, and is suitable for all kinds of large, medium and small computer environments. It is a highly efficient, reliable, and high-throughput database solution)
  3. Informix (is a relational database management system (RDBMS) family produced by IBM. As an integrated solution, it is set 4.SQL Server (Microsoft SQL Server is a comprehensive database platform that uses integrated business intelligence (BI) Tools provide enterprise-level data management. The Microsoft SQL Server database engine provides more secure and reliable storage functions for relational and structured data, allowing you to build and manage highly available and high-performance data applications for business )
  4. MySQL database (MySQL is a relational database management system developed by the Swedish company MySQL AB, which is a product of Oracle. MySQL is one of the most popular relational database management systems. In terms of web applications, MySQL is the best RDBMS (Relational Database Management System, one of the application software)
  5. PostgreSQL (PostgreSQL is a free software object-relational database management system (ORDBMS) with very complete features. It is an object-relational database management system based on POSTGRES, version 4.2 developed by the Department of Computer Science at the University of California. POSTGRES Many leading concepts appeared in commercial website databases only at a relatively late time. PostgreSQL supports most of the SQL standards and provides many other modern features, such as complex queries, foreign keys, triggers, views, transaction integrity, and multiple versions. Concurrency control, etc. Similarly, PostgreSQL can also be extended in many ways, such as by adding new data types, functions, operators, aggregate functions, indexing methods, procedural languages, etc.)
  6. Access database (Microsoft Office Access is a relational database management system released by Microsoft. It combines the two features of Microsoft Jet Database Engine and graphical user interface. It is a combination of Microsoft’s graphical user interface of database engine and software development tools. Database management system)

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