How to Use the Power BI DAX function UNION

What is the UNION Function?

The UNION function in DAX is used to combine two or more tables into a single table. This function is particularly useful when you have multiple tables with similar data structures that you want to combine into a single table. The resulting table will have all the columns from each table, with the data from each table appearing in its own set of rows.

How to Use the UNION Function in Power BI

To use the UNION function in Power BI, you will need to follow these steps:

Step 1: Open Power BI Desktop

The first step is to open Power BI Desktop. If you don’t have Power BI Desktop installed, you can download it for free from the Microsoft website.

Step 2: Add the Tables to Your Report

Once you have Power BI Desktop open, you will need to add the tables that you want to combine to your report. To do this, click on the “Get Data” button on the Home ribbon and select the type of data source that you want to use.

Step 3: Create a New Table

After you have added the tables to your report, you will need to create a new table that will contain the combined data. To do this, click on the “Modeling” tab and select “New Table” from the ribbon.

Step 4: Enter the DAX Formula

In the formula bar, enter the DAX formula for the UNION function. The syntax for the function is as follows:

NewTable = UNION(Table1, Table2, Table3, …)

In this formula, "NewTable" is the name of the new table that you want to create, and "Table1," "Table2," "Table3," and so on are the names of the tables that you want to combine.

Step 5: Run the Formula

Once you have entered the formula, you can run it by pressing Enter. The new table will be created, and you will be able to see it in the Fields pane.

Tips for Using the UNION Function

Here are a few tips for using the UNION function in Power BI:

- Make sure that the tables that you want to combine have the same structure. The columns should have the same data type and the same name.

- Be careful when you are combining large tables. The UNION function can be slow if you are working with a lot of data.

- If you want to combine tables that have different structures, you can use the UNION function in combination with other functions, such as ADDCOLUMNS and SELECTCOLUMNS.

The UNION function in DAX is a powerful tool that you can use to combine multiple tables into a single table in Power BI. With this function, you can create reports that incorporate data from multiple sources, making it easier to analyze and understand your data. By following the steps outlined in this article, you can start using the UNION function in your own Power BI reports.

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