Native cloud deployment on Azure is not available for this version of Exasol, but you can install Exasol as a Linux application on Azure instances. For more information, see Installation.

Native cloud deployment on Google Cloud is not available for this version of Exasol, but you can install Exasol as a Linux application on Google Cloud instances. For more information, see Installation.

APPROXIMATE_COUNT_DISTINCT

Purpose

This function returns the approximate number of distinct elements (without NULL).

Syntax

approximate_count_distinct::=

Approximate_Count_Distinct

Usage Notes

The result is not exact as it is with function COUNT, but it can be computed a lot faster.
For the calculation, the algorithm HyperLogLog is used internally.

Example

Copy

SELECT COUNT(DISTINCT customer_id) COUNT_EXACT,
APPROXIMATE_COUNT_DISTINCT (customer_id) COUNT_APPR
FROM orders WHERE price > 1000;

Result

COUNT_EXACT	COUNT_APPR
10000000	10143194