APPROX_COUNT_DISTINCT

Applies to: ✅ Data 360 SQL ✅ Tableau Hyper API

Computes an approximation of the count of distinct values with a specified expected relative error.

1approx_count_distinct(<expression> [, <error>])

• <expression>: An expression of any type to count distinct values for.

• <error>: A double precision value specifying the expected relative error. Must be in the range (0.002, 1]. Defaults to 0.023 (2.3% expected relative error).

Returns a bigint representing the approximate count of distinct values.

• Faster than exact count(distinct expression) for large datasets.
• The error parameter controls the trade-off between accuracy and performance.
• Lower error values provide more accurate results but may require more computation.

Get an approximate count of distinct values.

1SELECT approx_count_distinct(customer_id) AS approx_customers
2FROM orders;

Specify a custom error rate for higher accuracy.

1SELECT approx_count_distinct(product_id, 0.01) AS approx_products
2FROM sales;

Returns an approximate count with 1% expected relative error.

• COUNT
• Aggregate Functions