blocks|key|822876|text|使用XML创建需要发送到其他应用程序的文件。XML更适合作为数据交换格式而不是数据存储格式。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|822877|在使用XML时，下面的链接很容易描述：Why+should+I+use+XML+?|offset|length|822878|entityMap|0|LINK|mutability|MUTABLE|url|http://xml.silmaril.ie/whyxml.html^0|0|J|M|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

Use XML to create files that need to be sent to other applications. XML is more suited as data interchange format than as data storage format.

The following link is not bad to describe when using XML: <a href="http://xml.silmaril.ie/whyxml.html" rel="noreferrer">Why should I use XML ?</a>

blocks|key|818384|text|当您没有数据库(考虑单用户应用程序)或需要非常轻量级的存储格式时。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|818385|同样，正如前面提到的，一种交换格式。|818386|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Whenever you don't have the luxury of having a database (think single user applications) or need a very lightweight storage format.

Also as the previous poster mentioned, an interchange format.

blocks|key|822949|text|1)当您必须与他人交换数据时。XML是网络的"lingua+franca“--几乎每个人都可以阅读和解释它，这与数据库文件不同。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|822950|2)当你的数据量很小时，你不需要对它进行复杂的查询。XML文件很适合用来存储配置或文档模板。|822951|3)当你没有很多写入者试图访问相同的数据时。SQL数据库包含了在幕后为您工作的并发机制。SQL数据库可以支持索引来快速检索大型数据集上的信息……|822952|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Lingua_franca^0|N|D|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|U|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

1) When you have to interchange your data with others. XML is the "<a href="http://en.wikipedia.org/wiki/Lingua_franca" rel="noreferrer">lingua franca</a>" of the Web -- just about everyone can read and interpret it, unlike a database file. 

2) When your data volume is small and you don't have to do complex queries against it. XML files are good for things like storing configuration or document templates. 

3) When you don't have many writers trying to access the same data. SQL databases have involved concurrency mechanisms that are working behind the scenes for you. SQL databases can support indexes for the retrieval of information on large data sets quickly...

blocks|key|3131484|text|引用This+Book+(有效的XML:改进XML的50种具体方法)：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3131485|3131486|“XML不是一个数据库。它从来就不是一个数据库。它永远不会成为一个数据库。关系数据库是经过验证的技术，具有超过20年的实施经验。它们是坚固、稳定、有用的产品。他们不会消失的。XML是在不同数据库之间或数据库和其他程序之间移动数据的一种非常有用的技术。然而，它本身并不是一个数据库。不要像一个人一样使用它。“|blockquote|3131487|3131488|3131489|我认为这就是总结，尽管有点直截了当。XML是一种数据交换格式。可以有可以用XPath表达式查询DOM的XML解析库，但这与数据库管理系统不是一回事。您可以使用DOM/XPath接口构建DBMS，但要获得ACID属性或扩展到大型数据集，您需要实现DBMS引擎和具有索引、日志记录和DBMS其他工件的数据格式-这(根据定义)使其不同于XML。|3131490|entityMap|0|LINK|mutability|MUTABLE|url|http://www.amazon.com/exec/obidos/tg/detail/-/0321150406/102-0503816-7711357^0|2|9|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|D|3|-4|5|6|7|X|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|Y|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|10|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|11|8|@]|9|@]|C|$]]|$1|L|3|-4|5|6|7|12|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|S]]]]

To quote <a href="http://www.amazon.com/exec/obidos/tg/detail/-/0321150406/102-0503816-7711357" rel="noreferrer">This Book</a> (Effective XML: 50 Specific Ways to Improve Your XML):

<blockquote>
 “XML is not a database. It was never
 meant to be a database. It is never
 going to be a database. Relational
 databases are proven technology with
 more than 20 years of implementation
 experience. They are solid, stable,
 useful products. They are not going
 away. XML is a very useful technology
 for moving data between different
 databases or between databases and
 other programs. However, it is not
 itself a database. Don't use it like
 one.“
</blockquote>

I think this sums it up, if a little bluntly. XML is a data interchange format. One can have XML parsing libraries that can query a DOM with XPath expressions but that is not the same thing as a DBMS. You can build a DBMS with a DOM/XPath interface but to get ACID properties or scale to large data sets you need to implement a DBMS engine and a data format with indexes, logging and other artifacts of a DBMS - which (by definition) makes it something other than XML.

blocks|key|5387696|text|SQL是很好的表格数据--很容易放入行和列中的数据。XML适用于分层数据--具有不同大小的多个级别的数据。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5387697|SQL是很好的存储和搜索工具。XML对于传输和格式化是很好的。|5387698|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

SQL is good tabular data -- data that easily fits into rows &amp; columns.
XML is good for hierarchical data -- data which has several levels of different sizes.

SQL is good for storage &amp; searching.
XML is good for transmitting &amp; formatting.

blocks|key|3976722|text|XML和RDMS都可以用作数据存储，但每种实现都有自己的优点和缺点。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3976723|使用XML存储web应用程序的数据通常不是一个大问题，直到您开始处理大量数据，或者您决定要从数据中发现其他信息(例如:数据挖掘)。换句话说，为数据源存储大量的XML文件并不具有很强的伸缩性，但它使移动数据变得更容易。XML还可用于以非关系格式序列化复杂对象，如果可以直接从XML序列化/反序列化对象，则可以消除对ORM的需求|3976724|RDMSs+(数据库)通常更具可伸缩性，提供更大的并发支持，并且在处理大量数据时速度更快。关系模型使以后的数据挖掘变得更容易。数据库确实受到对象关系阻抗不匹配(http://en.wikipedia.org/wiki/Object-Relational_impedance_mismatch)的影响，这可能需要您编写丑陋的代码或使用复杂的ORM。|offset|length|3976725|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Object-Relational_impedance_mismatch^0|0|0|28|1T|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@$F|S|G|T|1|U]]|A|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]]]

Both XML and RDMSs can be used as datastores, but each implementation has its own advantages and drawbacks.

Using XML to store data for a web application is usually not a big problem until you start dealing with large amounts of data or you decide that you want to discover other information from your data (example: data mining). In other words, storing large amounts of XML files for a datasource is not very scalable but it makes it easier to move the data around. XML can also be used to serialize complex objects in a non-relational format, which could eliminate the need for an ORM if you can serialize/deserialize your objects directly from the XML

RDMSs (databases) are usually more scalable, offer greater concurrency support and are much faster when working with large amounts of data. The relational model makes it easier to data mine later on. Databases do suffer from the object-relational impedance mismatch (<a href="http://en.wikipedia.org/wiki/Object-Relational_impedance_mismatch" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Object-Relational_impedance_mismatch</a>) which might require you to write ugly code or use complex ORMs.

blocks|key|5387781|text|有些应用程序使用XML文件来存储配置，我更喜欢使用SQLite。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|5387782|entityMap|0|LINK|mutability|MUTABLE|url|http://www.sqlite.org/^0|P|6|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Some applications use XML files to store configuration, I prefer to use <a href="http://www.sqlite.org/" rel="nofollow noreferrer">SQLite</a> to do so.

blocks|key|3131675|text|如果我的主机上有有限的mysql数据库，那么我将看到使用XML作为数据存储的机会。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3131676|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I would go if I have limited mysql databases on my host, then I would see the opportunity for using XML as a datastore.

blocks|key|3131727|text|我永远不会使用任何类型的XML来存储数据。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3131728|我们使用XSLT转换作为SOA应用程序中的数据抽象层。所有对象都以XSLT格式相互发送数据，因此它们只需要理解一种语言。除了数据库连接器，它需要能够将数据转换为SQL，以便将数据发送到DB。|3131729|这样，您就不会将SQL字符串生成分布在应用程序中的无数个对象上。使维护变得更加容易。|3131730|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

I would never use any kind of XML to store my data.

We use XSLT transformations as a data abstraction layer in our SOA app. All objects send each other data in XSLT, so there is only one language they need to understand. Except for the database connector, which needs to be able to transform the data into SQL, for sending it to the DB.

This way you don't have SQL string generation distributed over a zillion objects in your app. Makes maintenance much easier.

blocks|key|3976937|text|下面是一个将XML与SQL结合使用的示例:经过身份验证的用户对不同的数据库进行读写操作，这些数据库并不都是相同的DBMS。公司A的用户使用本地SQL+Server数据库中的数据。公司B的用户使用来自远程Oracle数据库的数据。诸若此类。十几个不同的数据库，对于相同的基本数据，每个数据库的模式略有不同。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3976938|网站开发人员没有在远程数据库上创建存储过程的能力。SQL必须直接从web应用程序发送到数据库。由于每个数据库的SQL语法和模式略有不同，因此有必要对12个数据库中的每个数据库使用不同的SQL来执行相同的操作(SELECT、INSERT等)。|3976939|将SQL语句嵌入到web应用程序中的一种选择是将它们放在XML文件中。每个XML文件都包含十几个数据库中的一个数据库的SQL语句集。代码确定登录用户访问哪个数据库，并从指定的XML文件中检索适当的SQL。|3976940|与存储过程一样，可以在不停止或重新编译应用程序的情况下更新XML文件中的SQL。|3976941|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

Here is an example of using XML with SQL: Authenticated users read and write data to various databases, not all of which are the same DBMS. Users for Company A use data from a local SQL Server database. Users for Company B use data from a remote Oracle database. And so on. A dozen different databases, each with slightly different schemas for the same basic data.

The website developer does not have the ability to create stored procedures on the remote databases. SQL must be sent directly from the web app to the database. Since each database has a slightly different SQL syntax and schema, it is necessary to use different SQL for each of the 12 databases for the same operation (SELECT, INSERT, etc).

One of the choices for embedding the SQL statements in the web app is to place them in XML files. Each XML file contains the set of SQL statements for one of the dozen databases. The code determines which database is accessed for the logged-in user, and retrieves the appropriate SQL from the specified XML file.

Just as with stored procedures, the SQL in the XML file can be updated without stopping or recompiling the application.

blocks|key|3131932|text|我使用XML做的事情：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3131933|XSLT将数据从一个进程或机器持久化到另一个进程或机器。XSLT+|3131934|很少更改的|unordered-list-item|3131935|
|3131936|数据；配置设置等。将|3131937|3131938|作为XSLT的输入进行转换:一般来说，如果我的某个程序发出|3131939|3131940|，它就会使用XSLT进行转换，因此源数据将在某些|3131941|3131942|文本标记中表示为|3131943|
。(我们不要忘记这一点！)|3131944|这些用例和数据库的用例之间并没有太多的重叠。有一些，但不是很多。|3131945|具有讽刺意味的是，我目前使用XML最多的地方是在一个桌面应用程序中，该应用程序构建了一个内存中的ADO+DataSet，并使用DataSet的WriteXml和ReadXml方法来持久化和检索它。我之所以使用ADO，是因为使用ADO动态构建由元信息定义的数据模型要比为任务实现我自己的对象模型容易得多。|3131946|所以这里有一个看起来像是我使用XML作为数据库的案例。但我真的不是。我使用的对象模型恰好实现了许多类似数据库的功能，并且我使用XML作为其持久性格式。|3131947|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|13|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|14|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|15|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|16|8|@]|9|@]|A|$]]|$1|I|3|J|5|F|7|17|8|@]|9|@]|A|$]]|$1|K|3|H|5|6|7|18|8|@]|9|@]|A|$]]|$1|L|3|M|5|F|7|19|8|@]|9|@]|A|$]]|$1|N|3|H|5|6|7|1A|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|1B|8|@]|9|@]|A|$]]|$1|Q|3|H|5|6|7|1C|8|@]|9|@]|A|$]]|$1|R|3|S|5|F|7|1D|8|@]|9|@]|A|$]]|$1|T|3|U|5|6|7|1E|8|@]|9|@]|A|$]]|$1|V|3|W|5|6|7|1F|8|@]|9|@]|A|$]]|$1|X|3|Y|5|6|7|1G|8|@]|9|@]|A|$]]|$1|Z|3|10|5|6|7|1H|8|@]|9|@]|A|$]]|$1|11|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]]|12|$]]

Things I use XML for:

<ul>
<li>Persisting an object hierarchy.</li>
<li>Moving data from one process or machine to another.</li>
<li>Data that changes rarely, if at all; configuration settings and the like.</li>
<li>As the input to XSLT transforms: generally speaking, if one of my programs emits HTML, it's using XSLT to do it, and so the source data is going to represented as XML at some </li>
<li>Text markup. (Let's not forget that!)</li>
</ul>

There's not a whole lot of overlap between those use cases and the use cases for a database. Some, but not much.

Ironically, where I'm making my heaviest use of XML at the moment is in a desktop app that builds an in-memory ADO DataSet and uses the DataSet's WriteXml and ReadXml methods to persist and retrieve it. I'm using ADO because it's whole lot easier to dynamically build a data model defined by metainformation using ADO than it would be to implement my own object model for the task. 

So here's a case that looks like I'm using XML as a database. But I'm really not. I'm using an object model that happens to implement a lot of database-like functionality, and I'm using XML as its persistence format.

blocks|key|3977119|text|别。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3977120|试试SELECT+author+FROM+book|offset|length|3977121|entityMap|0|LINK|mutability|MUTABLE|url|http://www.joelonsoftware.com/articles/fog0000000319.html^0|0|2|N|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

Don't.

Try <a href="http://www.joelonsoftware.com/articles/fog0000000319.html" rel="nofollow noreferrer" title="Joel on Software: Back to Basics">SELECT author FROM book</a>

blocks|key|823236|text|我相信有相当多的商业应用程序大量使用XML作为存储介质。我为一个项目规划应用程序这样做过，在这个应用程序中，用户将每个项目存储在它自己的文件中。这个应用程序存储在U盘上，不需要安装。所有的数据都是从XML中提取出来的，并在内存中进行处理，所以getRecord(id)非常快。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|823237|所以我的回答是..当数据小到可以保存在内存中时，数据库就会被过度删除。|823238|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I believe there are quite a few commercial applications that make heavy use of XML as a storage medium. I've done it for a project planning application, where the user stores each project in it's own file. The app lives on a USB stick, and requires zero install. All the data is pulled from the XML and worked on in memory, so getRecord(id) is nuts fast. 

So my answer would be.. when the data is small enough to be held in memory, a database is over kill.

I've been working on database-driven web applications for a few years now and recently took on a project involving a CMS that is XML-capable. This has led me to think about the usage of XML/XSLT in general and in what situations it would be more useful than the approach I've always used, which is storing all of my data in a (My)SQL database and then using PHP/Python/etc. to work with it on the web as needed.

There's obviously something I'm not "getting" here.. could anyone give me examples of applications where storing the data in XML files instead of in a database would be preferable?

When would I use XML instead of SQL?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我从事数据库驱动的web应用程序已经有几年了，最近我参与了一个项目，该项目涉及一个支持XML的CMS。这促使我思考XML/XSLT的一般用法，以及在什么情况下它会比我一直使用的方法更有用，即将我所有的数据存储在(我的)SQL数据库中，然后根据需要使用PHP/Python/等在web上处理这些数据。很明显，这里有些东西我...

问什么时候我应该使用XML而不是SQL？
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