Data Analysis Expressions (DAX) is generally used with SQL Server Analysis Services - Tabular mode. In this chapter we will learn about some basics of DAX as well as the underlying engine that powers DAX.
Before we start understanding the key terms, it is highly recommended to have some basic experience of SSAS Tabular databases. This would make understanding and working with DAX easier.
What is SQL Server Analysis Services - Tabular Mode?
SQL Server Analysis Services is available in different server modes like Multidimensional and Data Mining, Tabular and PowerPivot.
What is the Vertipaq Engine?
Vertipaq in an in-memory columnstore engine introduced with SQL Server 2008 R2. In SQL Server 2012, this engine was enhanced with new in-memory analytics features and other capabilities and rebranded as xVelocity.
PowerPivot and SQL Server Analysis Services - Tabular mode (SSAS going forward) uses xVelocity engine which employs different features and algorithms for self-service and enterprise scale business intelligence respectively.
Using SSAS and SQL Server Data Tools (SSDT), one can create Business Intelligence Semantic Models (BISM). These models can also be referred to as Tabular models in the case of SSAS (Tabular)
These models can source data from multiple data sources which can be queried using the Data Analysis Expressions (DAX) language.
What is Data Analysis Expressions (DAX)?
SSAS loads data from BISM models into memory (RAM) in a proprietary format, also termed as data processing. A programming language is required to query and compute this data. DAX was introduced in 2010 to serve this purpose.
Below are some quick facts about DAX: