What are the databases under Linux?

The databases under Linux include: 1. Oracle; 2. MySQL; 3. MariaDB; 4. SQL Server; 5. Memcached, "Key-Value" type database; 6. Redis, "Key-Value" type Database; 7. MongoDB, etc.

The operating environment of this tutorial: Red Hat Enterprise Linux 6.1 system, Dell G3 computer.

What is a database?

A database is a warehouse that stores computer data. This warehouse organizes and stores data according to a certain data structure (data structure refers to the organizational form of data or the relationship between data). It can be Databases provide a variety of methods to manage the data within them.

Common relational databases under Linux

1. Oracle Database

Oracle, formerly known as SDL, was founded in 1977 by Larry Ellison and two other programmers. They developed their own flagship products and sold them in large quantities on the market. , In 1979, Oracle introduced the first commercial SQL relational database management system. Oracle is one of the earliest vendors to develop relational databases, and its products support the widest range of operating system platforms. Currently, Oracle's relational database products have one of the highest market shares.

Oracle (Oracle) is currently the world's largest database software company, and it is also a software provider and service provider with extremely rapid business growth in recent years.

Main application scope: traditional large enterprises, large companies, government, finance, securities, etc.

2. MySQL database

## The database is a small and medium-sized relational database management system. The software developer is Swedish MySQL AB company. exist 2008 Year 1 moon 16 No. quilt Sun Company acquisition, later Sun The company was again Oracle Takeovers. at present MySQL is widely used exist Internet Among the large, medium and small websites on the Internet, due to their small size, fast speed and low total cost of ownership, especially open source A characteristic, many large, medium and small websites choose to reduce the total cost of website ownership. MySQL As a website database, even national Taobao, a well-known website in China, also chose to abandon it. Oracle and replace it with a more open MySQL .

MySQL Main application scope of database: Internet field, large, medium and small websites, game companies, e-commerce platforms, etc.

3、MariaDB Database

MariaDB Database management system is MySQL A fork of the database, maintained primarily by the open source community. develop this MariaDB One of the possible reasons for the database branch is: Oracle acquired MySQL After that, there will be generals MySQL The potential of closed source Risk, therefore MySQL The open source community uses branching to avoid this risk. Develop MariaDB The database is designed to be fully compatible with MySQL Databases, including API and the command line, making it easy to become MySQL substitute for . On the storage engine side, use XtraDB (English: XtraDB ) instead of MySQL of InnoDB

MariaDB Depend on MySQL Founder of Michael Widenius (English: Michael Widenius ) leads the development, he earlier once 10 For a price of US$100 million, the company he founded MySQL AB Sold SUN , thereafter, with SUN Acquired by Oracle Purchase, MySQL The ownership of also falls into Oracle in the hands of MariaDB The name of the database comes from MySQL Founder of Michael Widenius 's daughter Maria name.

4、SQL Server database

Microsoft SQL Server It is a large-scale relational database system developed by Microsoft. 1987 In , Microsoft and IBM Completed cooperative development become OS/2 , IBM in which it is sold OS/2 Extended Edition Bind in the system OS/2 DatabaseManager , and micro There is still a lack of database products in the soft product line. To this end, Microsoft has set its sights on Sybase ,same Sybase signed a cooperation agreement to enable use Sybase The technology development is based on OS/2 The platform’s relational database. 1989 In , Microsoft released SQLServer1.0 Version. SQL Server It has comprehensive functions and high efficiency, and can be used as a database platform for medium-sized enterprises or units. SQL Server Can Windows The operating system is tightly integrated, both in terms of application development speed and system transaction processing operation. The running speed can be greatly improved. SQL Server The disadvantage of is that it can only be used in Windows system.

Main application scope: Some corporate e-commerce (CCTV shopping), use windows Server platform enterprise.

Non-relational database management systems commonly used under Linux

1. Memcached (Key-Value)

Memcached is an open source, high-performance caching system with distributed memory objects. It can reduce database load and accelerate dynamic Web Application, originally released by LiveJoumal of Brad Fitzpatrick exist 2003 Years of development completed. Currently, many users around the world are using it to build their own large-load websites or improve the response speed of their high-visited websites. Spend. Notice: Memcache is the name of this project, and Memcached is the main program file name on the server side.

The cache is generally used to save some frequently accessed objects or data (for example, the browser will cache frequently visited web pages. ), accessing objects or data through cache is much faster than accessing on disk. The former is memory and the latter is disk. Memcached is a pure memory caching system that caches frequently accessed objects or data in Memcached In the memory of , These cached data are passed by the program API is accessed in the form of , Memcached The data inside is like a huge HASH

Table, data starts with Key-Value The right way exists. Memcached By caching frequently accessed objects or data, it reduces the pressure of frequently reading the database and improves the response speed of the website. .

Official: http://Memcached.org/

Since Memcached is a pure memory caching software, all data will be lost once restarted. Therefore, Sina has developed an open source project MemcacheDB based on Memcached. By adding Berkeley DB's persistent storage mechanism and asynchronous primary and secondary replication mechanisms to Memcached, Memcached has transaction recovery capabilities, persistent data storage capabilities, and distributed replication capabilities. However, in recent years, it has been gradually replaced by other persistence products, such as Redis.

2. Redis (Key-Value)

Redis is a Key-Value type storage system. However, Redis supports relatively more storage value types, including string (string), list (linked list), set (collection) and zset (ordered set), etc. These data types support push/pop, add/remove, intersection, union, difference and richer operations, and these operations are all atomic. On this basis, Redis supports various different ways of sorting. Like Memcached, Redis data is cached in memory to ensure efficiency. The difference is that Redis will periodically write updated data to disk or write modification operations to additional record files, and on this basis, Master-Slave (master-slave) synchronization is achieved.

Redis is a high-performance Key-Value database. The emergence of Redis has largely compensated for the shortcomings of Key-Value storage such as Memcached, and can be a good supplement to relational databases in some situations. It provides PythonRuby, Erlang, and PHP clients, which are very convenient to use.

Official: http://www.Redis.io/documentation

                                                                              Features:

##3. MongoDB (Document-Web)

MongoDB is an intermediary The product that lies between relational databases and non-relational databases is the most feature-rich among non-relational databases and most similar to relational databases. The data structure it supports is very loose, similar to Json's Bjson format, so it can store more complex data types. The biggest feature of MongoDB is that it supports a very powerful query language. Its syntax is somewhat similar to an object-oriented query language. It can achieve almost most functions similar to single-table queries in relational databases, and it also supports indexing of data. It is characterized by high performance, easy deployment, easy use, and very convenient data storage.

The MongoDB server can run on Linux, Windows or OS X platforms, supports 32-bit and 64-bit applications, and the default port is 27017. It is recommended to run on 64-bit platform.

McmgoDB stores data in files (default path: /data/db).

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