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Applies to: 
Calculated column
Calculated table
Measure 
Visual calculation
Returns an estimated count of unique values in a column. This function invokes a corresponding aggregation operation in the data source, which is optimized for query performance, but with slightly reduced accuracy. This function can be used with the following data sources: Azure SQL, Azure Synapse dedicated SQL pool, BigQuery, Databricks, and Snowflake. This function requires DirectQuery mode. Import mode and dual storage mode are not supported.
Syntax
APPROXIMATEDISTINCTCOUNT(<columnName>)
Parameters
| Term | Description |
|---|---|
column |
The column that contains the values to be counted. This cannot be an expression. |
Return value
The approximate number of distinct values in column.
Remarks
The only argument to this function is a column. You can use columns containing any type of data. When the function finds no rows to count, it returns a BLANK, otherwise it returns the count of distinct values.