什么是 MDX 及其在 SAP BPC 中的用途
我想了解更多有关“MDX”（多维表达式）的信息。
它是什么？
它有什么用？
为什么要使用它？
它比 SQL 更好吗？
它在SAP BPS中有什么用（我没见过BPC，只是听说MDX在里面，想了解更多）？
I would like to know more about "MDX" (Multidimensional Expressions).
What is it?
What is it used for?
Why would you use it?
Is it better than SQL?
What is its use in SAP BPS (I haven't seen BPC, just heard that MDX is in it and want to know more)?
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MDX 是 Microsoft 开发的查询语言，用于其 OLAP 工具。自创建以来，其他人（开源项目 Mondrian 和 Hyperion）已尝试创建它的版本以在其产品中使用。
OLAP 数据往往看起来像星型模式，其中一个中心事实表被多个维度包围。 MDX 旨在允许您查询这些结构并创建交叉表类型结果。
虽然该语言看起来像 SQL，但其行为却并非如此，如果您是一名 SQL 程序员，那么心理上的飞跃可能会很困难。
至于它是否比SQL更好，它有一个高度专业化的目的，即分析特定格式的数据。因此，如果你想查询星型模式，最好是这样，否则，SQL 可能会完成这项工作。
MDX is the query language developed by Microsoft for use with their OLAP tools. Since its creation, others (The open source project Mondrian, and Hyperion) have tried to create versions of it for use in their products.
OLAP data tends to look like a star-schema with a central fact table surrounded by multiple dimensions. MDX is designed to allow you to query these structures and create cross-tab type results.
While the language looks like SQL it doesn't behave like it and if you are an SQL programmer, the mental leap can be tough.
As to whether it is better than SQL, it serves a highly specialized purpose, i.e. analyzing data in a specific format. So if you want to query a star schema, it is better, otherwise, SQL will probably do the job.
MDX 表示多维表达或类似的意思。它与 OLAP 多维数据集相关，而不是与 Oracle 或 SQL Server 等常规关系数据库相关（尽管某些 SQL Server 版本附带了 Analysis Services，即 OLAP）。多维世界涉及数据仓库和高效报告，而不是进行正常的事务处理，因此您不会将其用于订单输入系统，但您可以将该数据移动到数据集市中以运行报告以查看销售趋势。我希望这应该足以让你开始。
MDX means Multi Dimensional eXpressions or some such. It is relevant to OLAP cubes and not to regular relational databases such as Oracle or SQL Server (although some SQL Server editions come with Analysis Services which is OLAP). The multidimensional world is about data warehousing and efficient reporting, not about doing normal transactional processing so you wouldn't use it for an order entry system, but you might move that data into a datamart to run reports against to see sales trends. That should be enough to get you started I hope.
SQL 适用于“传统”数据库 (OLTP)。大多数人都很容易学习基础知识。
MDX仅适用于多维数据库（OLAP），在我看来比SQL更难学。问题是它们看起来非常相似。
许多程序员即使必须查询多维数据库也永远不需要MDX，因为大多数分析软件迫使他们使用拖放界面构建报告。
如果您没有使用多维数据库的要求，那么不要只是为了好玩而创建一个数据库......它不会......
SQL is for 'traditional' databases (OLTP). Most people learn the basics fairly easily.
MDX is only for multi-dimensional databases (OLAP), and is harder to learn than SQL in my opinion. The trouble is they look very similar.
Many programmers never need MDX even if they have to query multi-dimensional databases, because most analysis software forces them to build reports with drag-drop interfaces.
If you don't have a requirement to work with a multi-dimensional database, then don't create one just for the fun of it.....it won't be...
SAP-BPC（业务对象规划和合并）有 2 个版本
该产品的 Microsoft 分析服务版本允许您使用 MDX 或多维表达式来查询多维数据库（OLAP）并编写计算逻辑。
然而，SAP-BPC 的使用或管理不需要 MDX 知识。
您可以查看产品文档和演示。
祝你的研究好运，
There are 2 versions of SAP-BPC (Business Objects Planning and Consolidation)
The Microsoft analysis services version of the product allows you to use MDX or multi dimensional expressions to both query the multi-dimensional database (OLAP) and write calculation logic.
However, SAP-BPC does not require a knowledge of MDX to either be used or administered.
You can see product documentation and a demonstration.
Best of luck on your research,
专注于 SAP BPC：
它的用途是什么？
当您想要在许多记录/交叉点上以及提交原始数据后应用一些自定义计算/业务逻辑时，可以使用它。例如，首先在一个输入计划中发送价格，然后在另一个输入计划中发送数量，第三步根据所有产品的价格和数量运行销售额计算。
它还用于执行业务规则，因为您运行预定义的程序（如 CALC_ACCOUNT、CONSOLIDATION 等）
它比 SQL 更好吗？
在 BPC 中，“SQL”逻辑脚本比 MDX 具有更好的性能。然而，用于 BPC 目的的 SQL 与其他用途中使用的 SQL 没有太大关系，只是他们如何称呼它。
Focused on SAP BPC:
What is it used for?
It's used when you want to apply some custom calculation/business logic over many records/intersections and after submitting raw data. Example, first send prices in one input schedule, then quantities in other one, as a third step run a calculation for sales amount based on prices and quantities for all products.
It's also used to execute the Business Rules, for that you run a predefined program (like CALC_ACCOUNT, CONSOLIDATION, etc)
Is it better than SQL?
In BPC, "SQL" logic scripts have better performance than MDX. However SQL for BPC purposes has not much to do with SQL used in other it's just how they call it.
只需在顶部的搜索框中搜索 MDX，即可获得良好的开端。
You will get a good start by just searching for MDX in the search box up top.