Querying SQL Server Analysis Services

This section provides comprehensive documentation on how to query data from SQL Server Analysis Services (SSAS) using various languages and tools. Learn about MDX, DAX, and AMO for powerful data exploration and manipulation.

Key Querying Technologies

• Multidimensional Expressions (MDX)
• Data Analysis Expressions (DAX)
• Analysis Management Objects (AMO)

Multidimensional Expressions (MDX)

MDX is the primary query language for querying multidimensional data in SQL Server Analysis Services. It allows you to retrieve data from cubes, perform complex calculations, and analyze data from different perspectives.

MDX Fundamentals

• Understanding MDX Syntax
• Basic SELECT Statement Structure
• Working with Tuples and Sets
• Navigating Hierarchies and Levels

Advanced MDX Topics

• Calculated Members and Measures
• Scope and Assignments
• Error Handling in MDX
• Performance Optimization for MDX Queries

MDX Functions

Explore a comprehensive list of built-in MDX functions for:

• Set functions (e.g., Members, Children, Descendants)
• Aggregate functions (e.g., Sum, Avg, Count)
• String and Numeric functions
• Date and Time functions

MDX Query Examples

SELECT
    {[Measures].[Internet Sales Amount]} ON COLUMNS,
    {[Date].[Calendar Year].Members} ON ROWS
FROM
    [Adventure Works]
WHERE
    ([Product].[Product Category].&[1], [Customer].[Country].&[United States])

Data Analysis Expressions (DAX)

DAX is a formula expression language used in Power BI, Analysis Services tabular models, and Power Pivot in Excel. It's designed for relational data modeling and analytical computations.

DAX Introduction

• DAX vs. MDX
• Core Concepts: Tables, Columns, Measures
• Evaluation Contexts (Row Context, Filter Context)

DAX Functions

Learn about essential DAX functions for:

• Aggregation (e.g., SUM, AVERAGE, COUNTROWS)
• Filter functions (e.g., FILTER, ALL, CALCULATE)
• Time intelligence functions (e.g., DATESYTD, SAMEPERIODLASTYEAR)
• Relationship functions (e.g., RELATED, RELATEDTABLE)

Writing DAX Measures

Create powerful measures for your reports and analyses.

Total Sales = SUM('Sales'[SalesAmount])

Sales Last Year =
CALCULATE(
    [Total Sales],
    SAMEPERIODLASTYEAR('Date'[Date])
)

Analysis Management Objects (AMO)

AMO is a set of .NET classes that provide programmatic management of SQL Server Analysis Services instances and objects. It's used for automating administration tasks, deploying models, and managing SSAS databases.

AMO Basics

• Connecting to an Analysis Services Instance
• Exploring SSAS Objects (Databases, Cubes, Dimensions, etc.)
• Deploying and Processing SSAS Databases

AMO for Querying

While not a query language itself, AMO can be used to:

• Execute MDX and DAX queries programmatically.
• Retrieve query results.
• Manage query perspectives and roles.

Code Example (C# using AMO)

using Microsoft.AnalysisServices.AdomdClient;

// ...

string connectionString = "Provider=MSOLAP;Data Source=.;Initial Catalog=AdventureWorksDW2019;";
using (var connection = new AdomdConnection(connectionString))
{
    connection.Open();
    var command = connection.CreateCommand();
    command.CommandText = "SELECT {[Measures].[Internet Sales Amount]} ON COLUMNS FROM [Adventure Works]";

    using (var reader = command.ExecuteReader())
    {
        while (reader.Read())
        {
            Console.WriteLine(reader.GetValue(0));
        }
    }
}

Best Practices for Querying SSAS

• Understand your data model: Know your cubes, dimensions, measures, and relationships.
• Optimize your queries: Use efficient MDX/DAX constructs and avoid unnecessary complexity.
• Leverage aggregations and indexing.
• Monitor query performance and tune as needed.
• Use appropriate tools for the task (e.g., DAX Studio for DAX, SSMS for MDX).