Analysis Services Functions
SQL Server Analysis Services (SSAS) provides a rich set of functions for querying and manipulating multidimensional data (using Multidimensional Expressions - MDX) and tabular data (using Data Analysis Expressions - DAX). These functions are essential for creating complex calculations, performing data analysis, and building dynamic reports.
MDX Functions
MDX functions are used primarily with multidimensional models in Analysis Services. They enable powerful data retrieval and calculation capabilities. Below is a categorized overview of common MDX function types:
Set Functions
Manipulate sets of members, such as selecting specific members, filtering, or ordering.
Numeric Functions
Perform mathematical operations, aggregations, and statistical calculations.
String Functions
Manipulate text strings, used for formatting or concatenating data.
Date and Time Functions
Work with date and time values for time-based analysis.
Hierarchy Functions
Navigate and query hierarchies within dimensions.
Property Functions
Retrieve member properties, such as names, captions, or custom attributes.
Common MDX Examples:
SUM(): Aggregates values across a specified set.FILTER(): Returns a subset of members from a given set.TOPN(): Returns the top N members from a set.MEMBER(): Returns a member from a specified dimension.STRTOSET(): Converts a string into a set.
For a complete reference, please refer to the official MDX Function Reference.
DAX Functions
DAX functions are used in Power BI, SSAS Tabular, and Power Pivot for Excel. They are designed for relational data models and offer robust analytical capabilities.
Aggregation Functions
Perform aggregations like SUM, AVERAGE, MIN, MAX.
Date and Time Functions
Handle date and time intelligence, crucial for financial and temporal analysis.
Filter Functions
Modify the context in which expressions are evaluated, enabling dynamic filtering.
Information Functions
Check data types or identify errors.
Logical Functions
Perform conditional operations like IF, SWITCH.
Math and Trig Functions
Standard mathematical operations.
Relationship Functions
Navigate relationships between tables.
Statistical Functions
Calculate statistical measures like MEDIAN, STDEV.
Text Functions
Manipulate text strings.
Time Intelligence Functions
Perform calculations over periods like Year-to-Date, Quarter-to-Date.
Common DAX Examples:
CALCULATE(): Modifies the filter context for an expression.SUM(): Sums all the numbers in a column.AVERAGEX(): Calculates the average of an expression evaluated for each row in a table.RELATED(): Returns a related value from the 'one' side of a one-to-many relationship.TOTALYTD(): Returns a date that represents the last date of the year, based on the dates in the specified dates column.
For a comprehensive list and usage, please consult the official DAX Function Reference.
Mastering these functions is key to unlocking the full potential of SQL Server Analysis Services for business intelligence and data analysis.