Rule 4:- Treat duplicate non-uniform data as your biggest enemy

Focus and refactor duplicate data. My personal worry about duplicate data is not that it takes hard disk space, but the confusion it creates.

For instance in the below diagram you can see "5th Standard" and "Fifth standard" means the same. Now you can say due to bad data entry or poor validation the data has come in to your system. Now if you ever want toderive a report they would show them as different entities which is very confusing from end user point of view.

One of the solutions would be to move the data in to a different master table altogether and refer then via foreign keys. You can see in the below figure how we have created a new master table called as "Standards" and linked the same using a simple foreign key.

Rule 4：将重复、不统一的数据视作你最大的敌人

聚焦和重构复制数据。我比较担心的不是复制数据所需要的磁盘空间而是它因此而造成的混乱。

从下面的图表中，“5th Standard”和“Fifth standard”意思是相同的，你可以说是因为数据或者验证数据录入到你的系统原因，如果你想通过报表来显示他们的不同之处，从用户的角度开看，这是非常困难的。

其中一个解决方法就是将不同的任务栏把相同的数据通过新建一个键入值联接在一起。如图。我们通过创建一个新的条目“Standards”即可将数据重新排，显示相同的部分。