APPROX_COUNT_DISTINCT()

This function returns the approximate number of unique non-null values in a group.

Signature

APPROX_COUNT_DISTINCT ( expression )

Parameters

expression — An expression of any type, except image, sql_variant, ntext, or text.

Examples

SELECT APPROX_COUNT_DISTINCT(product) FROM dbo.orders;


--------------------
                   4

Run against SQL Server 16.0.4265.3 on 2026-09-13. This is the output we got, not the documentation’s.

Available on

SQL Server 2017 and later
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Microsoft Fabric warehouse
Fabric SQL database

Signature and description adapted from the Microsoft SQL documentation, used under the CC BY 4.0. SQL Server and Azure are trademarks of the Microsoft group of companies. This page is not affiliated with Microsoft.