DAX (Data Analysis Expressions) relationship functions in Power BI allow users to manage and navigate relationships between tables. These functions are essential for creating complex data models and ensuring accurate calculations across related tables.
Syntax:
RELATED(<column>)
Description:
Returns a related value from another table. This function is used to fetch values from a related table based on the existing relationships defined in the data model.
Example:
Consider the following two tables:
Sales Table
Products Table
We want to create a new calculated column in the Sales table called "ProductName" that fetches the product name from the Products table based on the ProductID.
Steps to Create the Calculated Column in Power BI Desktop
Ensure Relationship: Make sure there is a relationship between the Sales table and the Products table on the ProductID column. You can check this in the "Manage Relationships" dialog.
Open Power BI Desktop.
Load your data into the data model.
Go to the Data view by clicking on the table icon on the left pane.
Select the Sales table.
- Click on "New Column" in the Modeling tab.
- Enter the DAX formula into the formula bar
ProductName = RELATED(Products[ProductName])
- Press Enter to create the calculated column.
Result
The Sales table will now have an additional column called "ProductName":
In this example, the RELATED function fetches the ProductName from the Products table based on the ProductID for each row in the Sales table. This allows us to enrich the Sales table with information from the related Products table.
3. USERELATIONSHIP
Syntax:
USERELATIONSHIP(<column1>, <column2>)
Description:
Specifies an existing relationship to be used in a calculation. This function is useful when you have multiple relationships between tables and need to use a non-default relationship for a specific calculation.
Example:
Suppose you have multiple date columns (e.g., OrderDate and ShipDate) and want to calculate total sales by ShipDate:
TotalSalesByShipDate =
CALCULATE(SUM(Sales[SalesAmount]), USERELATIONSHIP(Sales[ShipDate], Dates[Date]))
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