# Power Pivot Principles: The A to Z of DAX Functions – HASONEFILTER

5 March 2024

*In our long-established Power Pivot Principles articles, we
continue our series on the A to Z of Data Analysis eXpression (DAX) functions. This week, we look at HASONEFILTER. *

* *

*The ***HASONEFILTER ***function*

The **HASONEFILTER **function is one of the information functions. It returns TRUE when the number of direct
filtered values on **columnName** is one; otherwise, it returns FALSE. It employs the following syntax:

**HASONEFILTER (columnName)**

This function has one parameter:

**columnName**: this is required and represents the name of an existing column, using standard DAX syntax and it cannot be an expression.

It has the following remarks:

- this function is similar to
**HASONEVALUE**function with the difference that**HASONEVALUE**works based in cross-filters while**HASONEFILTER**works by a direct filter - this function is not supported for use in DirectQuery mode when used in calculated columns or row-level security (RLS) rules.

Let’s
consider the following Table call **tbl_Example**:

We can write
a DAX to check if **Group** has only one [1] filter:

Then we may place this measure onto the PivotTable to check the result:

We can add
more inputs in the **tbl_Example**:

After refresh the Data Model the result is as follow:

We can use
this function inside the **CALCULATE**** **function:

The **CALCULATE** function will filter out the **tbl_Example** for value
“A” only then the **HASONEFILTER** will perform its function which give us
the following:

However, if
the filter context of **CALCULATE** has two [2] (or more) filters, even though the output data will
only contain “A”, the **HASONEFILTER** will output a FALSE result, *viz.*

It will output the following:

*Come back next week for our next post on Power Pivot in the **Blog** section. In the meantime, please remember we have
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