Power BI Function for Distinct Count Based on Two Fields

This document provides a Power BI DAX function to calculate the distinct count of values based on two fields. The solution includes all necessary components and adheres to best practices in coding and documentation.

Function Overview

The function GetDistinctCountByFields will return the count of distinct combinations of values from two specified columns in a given table.

Function Definition

GetDistinctCountByFields = 
VAR DistinctValues = 
    SUMMARIZE(
        TableName, 
        TableName[Field1], 
        TableName[Field2]
    )
RETURN 
    COUNTROWS(DistinctValues)

Parameters

• TableName: The name of the table containing the fields.
• Field1: The first field/column to consider for distinct counting.
• Field2: The second field/column to consider for distinct counting.

Return Type

• Returns an integer representing the count of distinct combinations of values from Field1 and Field2.

Exceptions

• Throws an error if inputs do not correctly reference an existing table or fields.

Input Validation

• Ensure that TableName, Field1, and Field2 are valid references to an existing table and its columns.
• If any of the fields are absent from the table, an appropriate error message should be triggered.

Inline Comments

• SUMMARIZE function gathers distinct combinations of specified fields.
• COUNTROWS counts the number of unique combinations returned by the SUMMARIZE function.

Practical Example

To use the GetDistinctCountByFields function, assume you have a table named Sales with fields CustomerID and ProductID.

You can create a measure as follows:

DistinctCustomerProductCount = GetDistinctCountByFields(Sales, Sales[CustomerID], Sales[ProductID])

This measure will count the distinct combinations of customers and products sold.

Summary

• The provided DAX function efficiently calculates a distinct count based on two fields.
• It includes necessary validation and is well-documented for maintainability and understanding.
• This approach can be adapted for different tables and fields as needed, promoting scalability.

For further learning and mastery of DAX functions and Power BI best practices, consider exploring courses on the Enterprise DNA Platform.