神马作文网急!高手来帮忙翻译下（关于数据库的）20分!
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急!高手来帮忙翻译下（关于数据库的）20分!
Domain Tables
Every time you have a column whose value most come from a known set of values you have a "domain" for that column. Your domain may be as simple as the day of the week (SUN, MON, THU .. SAT or 0, 1, 2 .. 6), as long as the Country Names or as unknown as the Books From The Catalog.
Sometimes you'll already have the need for a table representing these domain (a book as also an author, ISBN, publisher and etc) but sometimes the need for a table may not be so apparent.
If you just let your users type the country name, they can type "BRAZIL", "Brazil", "brazil" or "Brasil" (which is the name we Brasilians use for our country). Sometimes you can just force all input to upper or lower case, but most of the time you'll still be the subject of typing mistakes.
Domain tables solve this problem, by associating any ID (or code) to a name or description. The user will choose (or see on reports) the name/description, but the database tables will store the code.
You get also the benefits of faster queries, faster sorting (smaller strings, integers instead of strings, and so on), lower storage and ease of localization (do not need to change the code, just the table from which you get the descriptions).
Conclusion
Here we only touched the surface of Relational Database Design. I hope the info provided here will be useful to your work and I welcome any feedback about topics for future database, Java and Internet articles.
The article cited mSQL and SQL Anywhere, but you could apply the knowledge you (hopefully) got on mySQL, Solid, Oracle, DB2 and many other databases for OS/2 and other platforms.
A topic we will almost for sure cover soon is relational to object mapping. Although entities and collections (we've seen on the Java articles) are a very simple idea, thing become more complex when you take into account the relationships and joins.
Another nice topic would be Entity-Relationship modeling, but I know no easily trialable OS/2 tool for drawing E-R diagrams.
Domain Tables
Every time you have a column whose value most come from a known set of values you have a "domain" for that column. Your domain may be as simple as the day of the week (SUN, MON, THU .. SAT or 0, 1, 2 .. 6), as long as the Country Names or as unknown as the Books From The Catalog.
Sometimes you'll already have the need for a table representing these domain (a book as also an author, ISBN, publisher and etc) but sometimes the need for a table may not be so apparent.
If you just let your users type the country name, they can type "BRAZIL", "Brazil", "brazil" or "Brasil" (which is the name we Brasilians use for our country). Sometimes you can just force all input to upper or lower case, but most of the time you'll still be the subject of typing mistakes.
Domain tables solve this problem, by associating any ID (or code) to a name or description. The user will choose (or see on reports) the name/description, but the database tables will store the code.
You get also the benefits of faster queries, faster sorting (smaller strings, integers instead of strings, and so on), lower storage and ease of localization (do not need to change the code, just the table from which you get the descriptions).
Conclusion
Here we only touched the surface of Relational Database Design. I hope the info provided here will be useful to your work and I welcome any feedback about topics for future database, Java and Internet articles.
The article cited mSQL and SQL Anywhere, but you could apply the knowledge you (hopefully) got on mySQL, Solid, Oracle, DB2 and many other databases for OS/2 and other platforms.
A topic we will almost for sure cover soon is relational to object mapping. Although entities and collections (we've seen on the Java articles) are a very simple idea, thing become more complex when you take into account the relationships and joins.
Another nice topic would be Entity-Relationship modeling, but I know no easily trialable OS/2 tool for drawing E-R diagrams.
领土桌子
你有柱子谁的估价来自你适合这几次柱子有"领土"的套知名的价值的大多数. 作为象那些日子的一周的一样简单(Sun,星期四,星期一,你的领土的可能. 坐或者0,1,2. 6),象国名一样长或者从目录象那些书一样未知.
有时你已经将有对描述这些块领土为(作为也一名作者的一本书的一张桌子的需要, 出版商,ISBN 和等等)但是有时那些对桌子的需要可能不如此明显.
如果你刚刚让你的用户打印国名, 他们能打印"巴西", "巴西","brazil"或者"巴西"(在那些名字我们Brasilians适合我们的国家那里使用). 有时你可以对上面或者更低情况强迫全部输入,但是多数时间你仍然是打字错误的主题.
领土桌子解决这个问题,通过把任何身份证明(或者代码)和一个名字或者描述联系起来. 用户将选择(或者关于报告看见)名字/ 描述,但是数据库桌子将储存代码.
你也得到更快的质问的好处, 迅速分类(更小的线, 整数不是线,等等), 下部贮存和便于(不需要兑换代码,从哪个你得描述的桌子实在)的地方化.
结论
这里我们只接触相关的数据库的表面设计. 我希望在这里提供的信息将对你的工作有用,我欢迎任何关于将来的数据库,Java和因特网文章的题目的反馈.
文章在任何地方引用mSQL 和SQL, 但是你能使用知识你(充满希望)得到mySQL,可靠,Oracle,DB2和很多OS / 2的其他数据库, 以及其他平台.
我们几乎肯定将的一个题目盖子不久对目标映象相关. 虽然实体和收集(我们已经在爪哇文章上看见) 是一种非常简单的想法,当你考虑到关系并且参加时,事情变得更复杂.
另一个好的题目将是实体关系模型,但是我为画E-R 图解并不容易知道trialable OS / 2件工具.
你有柱子谁的估价来自你适合这几次柱子有"领土"的套知名的价值的大多数. 作为象那些日子的一周的一样简单(Sun,星期四,星期一,你的领土的可能. 坐或者0,1,2. 6),象国名一样长或者从目录象那些书一样未知.
有时你已经将有对描述这些块领土为(作为也一名作者的一本书的一张桌子的需要, 出版商,ISBN 和等等)但是有时那些对桌子的需要可能不如此明显.
如果你刚刚让你的用户打印国名, 他们能打印"巴西", "巴西","brazil"或者"巴西"(在那些名字我们Brasilians适合我们的国家那里使用). 有时你可以对上面或者更低情况强迫全部输入,但是多数时间你仍然是打字错误的主题.
领土桌子解决这个问题,通过把任何身份证明(或者代码)和一个名字或者描述联系起来. 用户将选择(或者关于报告看见)名字/ 描述,但是数据库桌子将储存代码.
你也得到更快的质问的好处, 迅速分类(更小的线, 整数不是线,等等), 下部贮存和便于(不需要兑换代码,从哪个你得描述的桌子实在)的地方化.
结论
这里我们只接触相关的数据库的表面设计. 我希望在这里提供的信息将对你的工作有用,我欢迎任何关于将来的数据库,Java和因特网文章的题目的反馈.
文章在任何地方引用mSQL 和SQL, 但是你能使用知识你(充满希望)得到mySQL,可靠,Oracle,DB2和很多OS / 2的其他数据库, 以及其他平台.
我们几乎肯定将的一个题目盖子不久对目标映象相关. 虽然实体和收集(我们已经在爪哇文章上看见) 是一种非常简单的想法,当你考虑到关系并且参加时,事情变得更复杂.
另一个好的题目将是实体关系模型,但是我为画E-R 图解并不容易知道trialable OS / 2件工具.