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 SQL Data Warehouse, BigQuery, Databricks, and Snowflake. This function requires DirectQuery mode. Import mode and dual storage mode are not supported.




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.


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.