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Linux下的主要数据库简介

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Jun 07, 2016 pm 04:53 PM

数据库是Linux应用中的主要部分。Linux上的主要数据库包括：商业数据库: Oracle、Sybase、DB2、Informix；自由软件数据库: MySQL

数据库是Linux应用中的主要部分。Linux上的主要数据库包括：商业数据库: Oracle、Sybase、DB2、Informix；自由软件数据库: MySQL、PostgreSQL、Msql等。

商业数据库

由于商业数据库有很好的技术支持，这里只简单介绍一下。

(1) IBM DB2 ()

(2) Informix () Informix目前支持Linux是Informix SE,ESQL/C,Connect.

(3) Oracle () Oracle 目前支持Linux的是Oralce 8i 、9i。

(4) Sybase () Sybase 目前支持Linux的是Adaptive Server Enterprise 11.9.2 。

(5)Ingres () CA目前支持Linux的是 Ingres II数据库.

自由软件数据库

1、MySQL

MySQL是瑞典的T.c.X公司负责开发和维护的，它是一个真正的多用户、多线程SQL数据库服务器。MysQL是以一个客户机／服务器结构实现其功能的，它由一个服务器守护程序mysqld和很多不同的客户程序和库组成。SQL是一种标准化的语言，它使得存储、更新和存取信息更容易。MySQL主要特点是快速、健壮和易用。MySQL的官方发音是“My Ess Que Ell”(不是MY-SEQUEL)。目前MySQL的最新版本是4.04，MySQL的网址是：，MySQL的标志是一个小海豚。见图－1。

图－1

（1）MySQL的优点：

1．它使用的核心线程是完全多线程，支持多处理器。

2．有多种列类型：1、2、3、4、和8字节长度自有符号／无符号整数、FLOAT、DOUBLE、CHAR、VARCHAR、TEXT、BLOB、DATE、TIME、DATETIME、 TIMESTAMP、YEAR、和ENUM类型。

3．它通过一个高度优化的类库实现SQL函数库并像他们能达到的一样快速，通常在查询初始化后不该有任何内存分配。没有内存漏洞。

4．全面支持SQL的GROUP BY和ORDER BY子句，支持聚合函数(COUNT()、COUNT(DISTINCT)、AVG()、STD()、SUM()、MAX()和MIN())。你可以在同一查询中混来自不同数据库的表。

5．支持ANSI SQL的LEFT 0UTER JOIN和ODBC。

6．所有列都有缺省值。你可以用INSERT插入一个表列的子集，那些没用明确给定值的列设置为他们的决省值。

7． MySQL可以工作在不同的平台上。支持C、C＋＋、Java、Perl、PHP、Python和TCL API。

（2） MySQL的缺点：

1、 MySQL最大的缺点是其安全系统，主要是复杂而非标准，另外只有到调用mysqladmin来重读用户权限时才发生改变。

2、 MySQL的另一个主要的缺陷之一是缺乏标准的RI（Referential Integrity-RI）机制；Rl限制的缺乏(在给定字段域上的一种固定的范围限制)可以通过大量的数据类型来补偿。

3、 MySQL没有一种存储过程(Stored Procedure)语言，，这是对习惯于企业级数据库的程序员的最大限制。

4、 MySQL不支持热备份。

5、 MySQL的价格随平台和安装方式变化。Linux的MySQL如果由用户自己或系统管理员而不是第三方安装则是免费的，第三方案则必须付许可费。Unix或Linux 自行安装免费、Unix或Linux 第三方安装 200美元，

需要一个应用组件 200美元。

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