Home Database Mysql Tutorial 【问】如何应对关系型数据库中列的不断增加

【问】如何应对关系型数据库中列的不断增加

Jun 07, 2016 pm 05:38 PM
Relational how response database

光看文章的题目可能很难明白我想说什么,还是先描述一下项目中遇到的问题吧。 我们项目中一张这样的表用来保存各种资源,假设为资源1、资源2等等,用ResGenre来标识。 我们可以认为资源类型是一个抽象的概念,资源1、资源2这些都是资源子类。一开始所有这些

光看文章的题目可能很难明白我想说什么,还是先描述一下项目中遇到的问题吧。

我们项目中一张这样的表用来保存各种“资源”,假设为资源1、资源2……等等,用ResGenre来标识。

我们可以认为资源类型是一个抽象的概念,资源1、资源2这些都是资源子类。一开始所有这些子类型都只有ResId,ResName等几个字段,一张ResInfo表就可以满足需求了。但是我们都知道项目千变万化,唯一不变的就是“变化”。随着业务的发展可能资源子类型越来越多,头疼的是原来的这张表的几个字段已经满足不了需求了,各个子类型的字段在不断扩充,最头疼的是它们加的字段都各不相同……这时该怎么办?

大概有以下几种办法:

 

单表继承

所谓单表继承就是所有的字段都保存在一张表上,增加字段时就扩充原来的表。

这种方法优点简单粗暴,当子类型很少以及子类型的特殊属性很少的时候还是可取的。但是如果子类型达到了10几个,而且子类型的字段很多时缺点也显而易见:冗余太多,某一行记录存在许多与当前子类无关的属性,而且页面管理起来也相当繁琐,每次增加一个字段的时候,所有子类型都受到影响。

 

每个子类型创建一个表

添加一个子类型就增加一张表。

     

   ……

两个子类型存储完全独立,,每增加一张表页面就要重新管理一张表,子类型很多的时候这种方式也不是很好。

 

多表继承

既有基表,又有子类型表,就像面向对象里面的继承。

多表继承的方式可以减少字段的冗余,但是同样的子类型很多时,表较多,管理起来比较麻烦。

 

半结构化数据模型

如果有很多子类型或者必须经常增加新的字段支持,那么可以用一个BLOB列来存储数据,用XML或者JSON格式。

 Property是一个属性列:它可以用Json来存储额外增加的字段:同时包含了字段名字和值。

{ "Field1":"Value1","Field2":"Value2" }

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