想要改进这个问题吗? 更新了问题 ,因此堆积溢流为
Closed 10 years ago.
我需要创建一个代表所有货币的数据库表格结构, 如果任何一国货币的等级等级超过两个等级, 我就必须创建一个自我参考表格。 但如果所有货币只有两个等级( 如Dollar> Cent, Rupees> Paisa 等), 那么我只能用同一表格的两列来代表它, 包括父子关系和子女关系。
有谁知道世界上所有货币是否总是只有两个等级?
这不是一个有关编程的问题.但根据维基百科http://en.wikipedia.org/wiki/List_of_circularation_curreance ,这不是一个有关编程的问题。
换句话说,世界上所有货币都有两个等级。 有一天,一个国家引入了第三个等级,而你的所有设计都假设所有货币都有两个等级,但这一设计并不正确。
我认为你应该有一个国家表:
国家(ID,名称)
您应该有一个货币表:
货币(ID、国家ID、父母身份、统一、签名)
以美元表示的国产总值是美元,用美元表示的国产总值是美元。 您需要将国家与货币区分开来,因为有的国家拥有一种以上的货币,特别是引进欧元和使用旧货币的国家。
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