Additionally, be prepared to use a text editor to create the sample queries as presented in this chapter. However, the instructions in this chapter use the MaxL Shell. In this section you will create a template to use as a basis for developing simple queries. In the above query, the set is empty, but the braces remain How To Write Mdx Queries a placeholder. To create a query template:. Create a folder to store sample queries that can be run against the Sample.
MDX from the editor instead. A set is an ordered collection of one or more tuples that have the same dimensionality see Rules for Specifying Sets for an explanation of dimensionality. A tuple is a way to refer to a member or a member combination from any number of dimensions.
For example, in the Sample. If the member name starts with number or contains spaces, it should be within brackets; for example, . Brackets are recommended for all member names, for clarity and code readability. By specifying dimension name or any one of the ancestor member names as a prefix to the member name; for example, [Product].
This is a recommended practice for all member names; it eliminates ambiguity and enables you to refer accurately to shared members. Use no more than one ancestor in the member name qualification.
Essbase returns an error if multiple ancestors are included. By specifying the name of a calculated member defined in the WITH section. In this exercise, we will add a set to the query and run it. To run the query:. How To Write Mdx Queries a set can be as simple as one tuple, add Jan as a set to the query template. Retain the braces required for all set specifications except for sets that are produced by a function call. The examples in this chapter use the MaxL Shell.
Start the MaxL Shell and log in with a valid user name and password. Enter a semicolon at the end, anywhere after Basic but before pressing Enter.
The semicolon is not part of MDX syntax requirements, but it is required by MaxL Shell to indicate the end of a statement that is ready to execute.
As described previously, a set is an ordered collection of one or more tuples.
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Rather, , [Actual] represents a tuple consisting of members from two dimensions, Product and Scenario. When a set has more than one tuple, the following rule applies: In each tuple of the set, members must represent the same dimensions as do the members of other tuples of the set.
Additionally, the dimensions must be represented in the same order. In other words, each tuple of the set must have the same dimensionality.
Note. For more information about performance issues related to MDX queries and calculations, see the section “Writing Efficient MDX” in the SQL Server Download MDX queries - KB; Introduction. In this article, we will go through some basic concepts and terminologies used while writing MDX Queries on your OLAP. Speaking from personal experience, learning and comprehending how to write MDX queries for SQL Server Analysis Services was difficult after spending years writing. The basic Multidimensional Expressions (MDX) query is the SELECT statement—the most frequently used query in MDX. By understanding how an MDX SELECT statement must. In this tutorial, you can learn how to write MDX Queries in Analysis Services (SSAS). Click to check out more!.
For example, the following set consists of two tuples of the same dimensionality. The following set breaks the dimensionality rule, because Feb and Sales are from different dimensions.
The following set breaks the dimensionality rule, because although the two tuples contain the same dimensions, the order of dimensions is reversed in the second tuple.
A set can also be a collection of sets, or it can be empty containing no tuples.
Analysis Services and MDX Essentials with Paul Turley
An axis is a specification determining the layout of query results from a database. Axes fit into MDX queries as follows:. Using more than three axes is uncommon. The order of axes is not important; however, when a set of axes 0 through n are specified, no axis between 0 and n should be skipped.
Additionally, a dimension cannot appear on more than one axis. To run a two-axis query:. As the set specification for the column axis, enter the Product members and These member names contain special characters, so you must use brackets. For example, add the text shown in bold:. The convention used here, to enclose all member names in brackets even if they do not contain special characters, is recommended. Paste the query into the MaxL Shell and run it, as described in Exercise 2: Running Your First Query.
Querying Multiple Dimensions on a Single Axis. To query multiple dimensions on a single How To Write Mdx Queries. On the column axis, specify two tuples, each of which is a member combination rather than a single member. Enclose each tuple in parentheses, because more than one member is represented in each tuple.
A cube specification is the part of the query that determines which database is being queried. The cube specification fits into an MDX query as follows:.
Rather than creating sets member-by-member or tuple-by-tuple, you can use a function that returns a set. MDX includes several functions that return sets and several functions that return other values. The MemberRange How To Write Mdx Queries returns a range of members inclusive of and between two specified members of the same generation.
Its syntax is as follows:. The layertype argument is optional. See the Oracle Essbase Technical Reference. An alternate syntax for MemberRange is to use a colon between the two members, instead of using the function name: To use the MemberRange function:. Here CrossJoin function returns the cross product of two sets from different dimensions. The CrossJoin function takes two sets from different dimensions as input and creates a set that is a cross product of the two input sets, useful for creating symmetric reports.
To use the CrossJoin function:. Add two comma-separated pairs of braces as placeholders for the two set arguments you will provide to the CrossJoin function:. In the first set, specify the Product member How To Write Mdx Queries. When using CrossJoin, the order of arguments affects the order of tuples in the output.
The Children function returns a set of all child members link the given member. An alternate syntax for Children is to use it like an operator on the input member, as follows: We will use the operator syntax in this exercise.
To use the Children function to introduce a shortcut in the first axis specification:. In the second set of the column axis specification, replace [East],[West],[South],[Central] with [Market].
You should see the same results as were returned for Exercise 6: Using the CrossJoin Function. In MDX, layer refers to generations and levels in an Essbase hierarchy. In Essbase, generation numbers begin counting with 1 at the dimension name; higher generation numbers are those closest to leaf members in a hierarchy.
Level numbers begin with 0 at the leaf-most part of the hierarchy, and the highest level number is a dimension name. A number of MDX functions take a layer you specify as an input argument and perform set operations based on the generation or level represented in the layer argument. Generation or level name; for example, States or Regions.
The dimension name along with the generation or level name; for example, Market. The Levels function with a dimension and a level number as input. The Level function with a member as input. Level returns the level of quarters in Sample.
Basic, which is level 1 of the Market dimension. The Generations function with a dimension and a generation number as input. The Generation function with a member as input. Generation returns the generation of quarters in Sample. Basic, which is generation 2 of the Market dimension. Basic database, Qtr1 and Qtr4 are in the same layer. This means that Qtr1 and Qtr4 are also in the same generation. However, in a different database with a ragged hierarchy, Qtr1 and Qtr4 might not necessarily be in the same level, although they are in the same generation.
For example, if the hierarchy of Qtr1 drills down to weeks, and the hierarchy of Qtr4 stops at months, Qtr1 is one level higher than Qtr4, but they are still in the same layer. The Members function can be used to return all members of a specified generation or level.
Its syntax when used with a layer argument:. To use the Members function:. Use the Members function and the Levels function to select all level 0 members How To Write Mdx Queries the Market dimension of Sample.