DAX Function Utilizing CROSSJOIN

Introduction

This documentation guides you through writing a DAX function that uses the CROSSJOIN function to create all combinations of rows from two tables. The instructions include comments, input validation, and a practical example for ease of understanding.

Function Explanation

Purpose

The function combines every row from two tables, generating a Cartesian product. This is useful for scenarios where all possible combinations of two datasets are needed for analysis.

Inputs

• Table1: The first table to use for the cross join.
• Table2: The second table to use for the cross join.

Output

• A table that contains the Cartesian product of Table1 and Table2.

Parameters

The function doesn't have explicit parameters but operates on table variables within a DAX formula context.

DAX Function with Cross Join

/**
 * Function: CrossJoinTables
 * Purpose: Create a Cartesian product of two tables.
 * Inputs: Two tables (Table1, Table2)
 * Output: A table combining all rows from both input tables.
 * Example Usage: 
 *  CROSSJOIN(
 *      ADDCOLUMNS(Table1, "Key", [Column1]),
 *      ADDCOLUMNS(Table2, "Value", [Column1])
 *  )
 */

CrossJoinTables = 
VARIABLE Table1 = 
    SELECTCOLUMNS(
        YourFirstTable,
        "Column1", [Column1]
    )
    
VARIABLE Table2 = 
    SELECTCOLUMNS(
        YourSecondTable,
        "Column2", [Column2]
    )

RETURN
    // Cross-join the two tables and return the result
    CROSSJOIN(Table1, Table2)

Commentary and Explanation:

1. Data Preparation:

   • The SELECTCOLUMNS function is used to filter the necessary columns from the input tables.

2. Cross Join:

   • CROSSJOIN(Table1, Table2) creates the Cartesian product of the rows from Table1 and Table2.

Practical Example

Suppose we have two tables with the following data:

Using the DAX Function

CrossJoinExample = 
VAR Table1 = 
    SELECTCOLUMNS(
        DataTable1,
        "Column1", [Column1]
    )
    
VAR Table2 = 
    SELECTCOLUMNS(
        DataTable2,
        "Column2", [Column2]
    )

RETURN
    // Using the CROSSJOIN function to combine the two tables
    CROSSJOIN(Table1, Table2)

Output:

Summary

This guide assists in creating a DAX function to generate a Cartesian product using CROSSJOIN. Follow the instructions and adapt the variables as required for your particular dataset.

For additional learning and a more in-depth understanding of DAX and data analysis techniques, consider exploring courses on the Enterprise DNA Platform.