APPROXIMATEDISTINCTCOUNT DAX Function (Aggregation)

Counts the approximate number of distinct values in a column. Currently this function is only available on a DirectQuery table from Azure SQL or Azure SQL Data Warehouse.

Syntax

APPROXIMATEDISTINCTCOUNT ( <ColumnName> )
Parameter Attributes Description
ColumnName

The column for which the distinct values are counted.

Return values

Scalar A single integer value.

The approximate number of distinct values in ColumnName.

Remarks

The SQL query generated uses the APPROX_COUNT_DISTINCT in Transact-SQL to obtain the result.

» 2 related functions

Examples

--  APPROXIMATEDISTINCTCOUNT can be used only in models using DirectQuery
--  on Azure SQL or Azure SQL Data Warehouse.
--  It uses the faster (but less accurate) version of DISTINCT available 
--  on these engines to compute distinct counts: APPROX_COUNT_DISTINCT 
--  The function implementation guarantees up to a 2% error rate within 
--  a 97% probability.
DEFINE
    MEASURE Sales[#Prods] = DISTINCTCOUNT ( Sales[ProductKey] )
    MEASURE Sales[#App Prods] = APPROXIMATEDISTINCTCOUNT ( Sales[ProductKey] )
EVALUATE
SUMMARIZECOLUMNS (
    'Date'[Calendar Year],
    TREATAS ( { "CY 2007", "CY 2008", "CY 2009" }, 'Date'[Calendar Year] ),
    "#Prods",       [#Prods],
    "#App Prods",   [#App Prods]
)

Related functions

Other related functions are:

Last update: Feb 24, 2021   » Contribute   » Show contributors

Contributors: Alberto Ferrari, Marco Russo, Kenneth Barber

Microsoft documentation: https://docs.microsoft.com/en-us/dax/approximate-distinctcount-function-dax

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Context Transition

This function performs a Context Transition if called in a Row Context. Click to read more.

Row Context

This expression is executed in a Row Context. Click to read more.

Iterator

Not recommended

The use of this function is not recommended. See Remarks and Related functions for alternatives.

Not recommended

The use of this parameter is not recommended.

Deprecated

This function is deprecated. Jump to the Alternatives section to see the function to use.

Deprecated

This parameter is deprecated and its use is not recommended.

DirectQuery compatibility

Limitations are placed on DAX expressions allowed in measures and calculated columns.
The state below shows the DirectQuery compatibility of the DAX function.

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