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MySQL学习笔记-数据库概述及MySQL简介_MySQL

Jun 01, 2016 pm 02:11 PM
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  数据库是与日常应用紧密相连的,在没有出现数据库之前,人们通过手工记录处理各种信息。当需要记录处理的信息非常多时,手工处理效率就显得及其低下了。比如病人到医院就医,需要通过挂号、就诊、买药、住院、治疗、康复等一系列程序。挂号就要登记病人姓名、性别、年龄等情况。买药的时候医院依据药单从成千上万种药物中挑出符合要求的药品,需要知道药的品名、具体位置、库存多少、存取多少等等。如果病人很多,医院选药就很复烦了。如果手工处理,工作量大,而且有可能调拿错药。这时如果通过数据库处理,只需简单地输入药品名就马上可以知道具体位置、库存还有多少等详细情况。这样是不是很方便、提高了效率,并且还避免了拿错药的情况。
  
  数据库(DataBase)的优越性只在组织和管理的信息很庞大或很复杂,用手工处理极为繁重时才能显示出来。当然,每天处理数百万个业务的大公司可以使用数据库。但是,即使只涉及个人爱好的单一人员维护信息的小公司也可能会需要数据库。不难想像如果有下列情况出现,使用数据库会带来更多的好处:
  
  ■ 您的公司有几百个员工。需要保存每个员工的个人情况和工资记录,以便知道给谁付过工资,什么时候付的,并且必须对这些记录进行汇总以便能向税务部门报收益表。还需要明了您的公司雇人所做的工作以及对每项工作所做的安排。
  
  ■ 您是个教师,需要知道学分和出勤情况。每当您进行测验或考试时,都要记录学生们的学分。将考试成绩写在学分簿上很容易,但以后利用这个学分簿却很费事,需要一页页地翻查。即便是要统计出每个学生的缺旷课情况也不是一件简单的事。
  
  通常我们利用数据库管理系统来处理诸如人们用文件柜来完成的那样一类的任务。确实在某种意义上说,数据库就像一个大文件柜,只不过是一个内建的文件编排系统而已。电子化处理记录相对手工处理记录有很多优点。例如,如果您在某种保存有客户记录的办公设施内工 作,那么数据库管理系统可在某些方面向您提供帮助:
  
  ■ 减少记录编档时间。不必为寻找增加新记录的位置而查看橱柜的所有抽屉。只要将记 录放入文件编排系统,并令文件编排系统为您将该记录放入正确的位置即可。
  
  ■ 减少记录检索时间。在查找记录时,不需要自己去寻看每个记录以找到含有所需信息的那个记录。假如您在一个牙科诊所中工作。如果想给所有近来未到诊断做过检查的病人发催询单,只需要求文件编排系统查找合适的记录即可。当然,这样做会有别于 吩咐别人去做。吩咐别人去做,您只需说,“请确定哪些病人最近6 个月内没来过。”
  
  数据库应用系统主要包括数据库(DataBase,简称DB)、数据库管理系统(DataBase Management System,简称DBMS)、数据库应用3大部分。这3部分之间的关系如图2.1所示。
  
  MySQL学习笔记-数据库概述及MySQL简介_MySQL
  
  实际的数据库可能相当复杂,对数据库的操作就更加复杂。我了更有效地管理和操作数据库,人们研制出数据库管理系统(DataBase Management System,简称DBMS)。DBMS是人们用于操作数据库的软件产品。我们平常说的数据库Oracle、MS SQL Server、MySQL、Sybase、FoxPro、Access等等,都是属于DBMS范畴。虽然这些DBMS产品的功能各有所异,但是基本功能到大同小异差不多。
  
  MySQL是现在流行的关系数据库中其中的一种,相比其它的数据库管理系统(DBMS)来说,MySQL具有小巧、功能齐全、查询迅捷等优点,关键的是它是免费的,可以在Internet上免费下载到,并可免费使用,对于一般中小型,甚至大型应用都能够胜任。
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