Join Our Global Community Join our email list and receive the latest case studies, event updates, product news, and much more. Idera uses cookies required, functionality, and advertising cookies to improve user experience. By using our website you consent to all cookies in accordance with our Cookie policy. An OLAP database is often an aggregation of a relational database; as a result, you can write MDX queries to retrieve key calculations that measure company performance, often with less code than standard SQL.
If you want to RANK a result set based on an order, first create an ordered set and then create a calculated member that applies the RANK function against the ordered set. This will usually provide maximum performance. See the end of this article for recommended references. Over the last few years, Microsoft has made serious advancements in the areas of business intelligence and OLAP databases. Here are some examples where MDX comes into play:.
Many tools that use MDX will offer designers that generate basic MDX syntax; however, you may still need to modify or customize the generated syntax to address specific requirements.
Recently, a CoDe Magazine subscriber approached me at a community event and asked me why I always include thirteen tips. The story symbolizes the providence of giving as much as you can. Before I begin, I want to make a special thanks to Mr.
Deepak Gupta. In writing this article, I needed to research some material and post some questions online, and Deepak was able to answer my questions. Deepak, you really know your stuff! Here are some starter queries to help you get a feel for MDX. This first query retrieves sales amount by Customer State. Of course, many MDX queries will need to return multiple measures, broken out by multiple dimensions.
Most results sets need to be sorted in a particular order. Notice one thing: The results are sorted by sales descending, within the state. The first few MDX queries I discussed in this article retrieved existing measures. However, many queries need to return calculations based on existing measures for example, per unit calculations, percentages, etc. A SET is essentially a collection usually an ordered collection of members i.
Many MDX queries use calculated members and sets together. Suppose you want to sort on a calculated member. So how do you use MDX to filter based on specific conditions? Here is an example:. Name convention. If you return to design mode, the designer tool will overwrite your custom changes. Suppose you want to rank sales by product, according the sales amount descending so that the top-selling product is ranked 1, etc. CurrentMember and the ordered set against which each subcategory currentmember is evaluated.
That covers a basic example. But suppose you want to rank product sales within customers? Or suppose you want to rank product sales across all products and customers? Tip 7 will cover this in more detail. Finally, if you want to retrieve the states that make up the top ten million dollars in sales, you can use the TOPSUM function. You will usually use it when you need to combine sets of data. Software Engineering Stack Exchange is a question and answer site for professionals, academics, and students working within the systems development life cycle.
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But why go on to the trouble of creating a new completely different language when you could build on SQL, extend it to add the features needed by OLAP applications? Each database vendor has their own set of proprietary SQL extensions to achieve certain piecemeal goals.
But none of these extensions have achieved widespread adoption like SQL has. If your goal is to create enhanced functionality in a standards-based way, you have two options. You can either go to the SQL standards committee and make your case which could take years , or you can create your own standard and hope the community adopts it. Vendor extensions on the SQL standard have not succeeded in this way. So Microsoft, instead of taking a piecemeal approach, decided to go all in and create a comprehensive solution.
And it worked; the industry adopted it as the go-to solution for OLAP querying. Ergo, a defacto standard, without the committee pain. MDX is a de-facto standard , created by a single vendor. Assuming you can get broad buy-in, you have eliminated the need for design by committee, and saved yourself a lot of time, effort and money.
They are somewhat different I've no experience with them, so the details escape me at present , and a different mental model is useful for interacting with them even if it's really a relational DB underneath. The problem you are running into is that you're seeing the OLAP database as a relational DB, and so you want to use the appropriate language SQL to query the relational database. I've been heavily involved in this and have had some trouble picking up certain bits of MDX. That said, I think it's unfair to brand MDX as unnecessary.
It does provide benefits, but only if you don't try to use it like you would SQL. Indeed, the reason it's tricky to pick up is because often there isn't a direct equivalent in SQL, so you're trying to learn the idea as well as the syntax. There's an unhelpful vein of thought among some team members when it comes to retrieving data: OLAP cubes are an "upgrade" over traditional SQL tables.
Seeing the two as equivalent or different versions of the same thing isn't helpful, at least conceptually in my experience. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
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