How does the APPROXIMATEDISTINCTCOUNT function (DAX) work?
The APPROXIMATEDISTINCTCOUNT function (DAX) counts the approximate number of distinct values within a column.
APPROXIMATEDISTINCTCOUNT Formula Syntax
How do you use the APPROXIMATEDISTINCTCOUNT function?
When compared with DISTINCTCOUNT, this function can query a large amount of data with better performance and with a slight deviation from the exact result.
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Considerations when using the APPROXIMATEDISTINCTCOUNT function
The only argument to this function is a column that contains the values that need to be counted. This cannot be an expression.
You can use columns containing any type of data. When the function finds out that there are no rows to count, it will return BLANK; otherwise it will return the count of distinct values.
Currently, this function is used on a DirectQuery table from Azure SQL or Azure SQL Data Warehouse.