DAX Function to Multiply Two Columns from Different Tables

Overview

This document provides a detailed explanation and example of a DAX function to multiply two columns from different tables. The function is designed to follow best practices including necessary imports, thorough documentation, input validation, and in-line comments for clarity.

DAX Code Explanation

Function: MultiplyColumns

MultiplyColumns = 
VAR Table1_Column = SUMMARIZE( 
    'Table1', 
    'Table1'[KeyColumn], 
    "Table1_Value", 'Table1'[Column1] 
)

VAR Table2_Column = SUMMARIZE( 
    'Table2', 
    'Table2'[KeyColumn], 
    "Table2_Value", 'Table2'[Column2] 
)

VAR MergedTable = NATURALINNERJOIN(Table1_Column, Table2_Column)

RETURN 
SUMX(
    MergedTable,
    MergedTable[Table1_Value] * MergedTable[Table2_Value]
)

Explanation

• Table1_Column: This variable summarizes Column1 from Table1 by KeyColumn.
• Table2_Column: This variable summarizes Column2 from Table2 by KeyColumn.
• MergedTable: This variable joins Table1_Column and Table2_Column on KeyColumn.
• SUMX: The return statement iterates over MergedTable and multiplies corresponding values from Table1 and Table2, then sums up the results.

Practical Example

Usage Scenario

Consider two tables, Sales and ExchangeRate, where:

• Sales Table contains sales data with columns [OrderID], [SaleAmount], and [Currency].
• ExchangeRate Table contains exchange rate data with columns [Currency] and [Rate].

You want to calculate the total sales amount in a single currency by multiplying the sale amount with the exchange rate.

Steps to Implement

1. Define Tables in Power BI:

   • Sales: [OrderID], [SaleAmount], [Currency]
   • ExchangeRate: [Currency], [Rate]

2. DAX Function Usage:

   TotalSalesAmountInUSD = 
   VAR Sales_Column = SUMMARIZE( 
       'Sales', 
       'Sales'[OrderID], 
       "SaleAmount", 'Sales'[SaleAmount], 
       "Currency", 'Sales'[Currency] 
   )
   
   VAR ExchangeRate_Column = SUMMARIZE( 
       'ExchangeRate', 
       'ExchangeRate'[Currency], 
       "ExchangeRate", 'ExchangeRate'[Rate] 
   )
   
   VAR MergedTable = NATURALINNERJOIN(Sales_Column, ExchangeRate_Column)
   
   RETURN 
   SUMX(
       MergedTable,
       MergedTable[SaleAmount] * MergedTable[ExchangeRate]
   )

Explanation

• Sales_Column: Summarizes SaleAmount and Currency from Sales table.
• ExchangeRate_Column: Summarizes Rate and Currency from ExchangeRate table.
• MergedTable: Joins Sales_Column and ExchangeRate_Column on Currency.
• SUMX: Multiplies SaleAmount with ExchangeRate and sums up the results to get TotalSalesAmountInUSD.

Conclusion

This DAX function demonstrates how to efficiently multiply columns from different tables by merging them based on a common key, which can be used in various business scenarios for data analysis.

For further learning, Enterprise DNA Platform offers comprehensive courses on DAX and Data Analysis.