APPROX_COUNT_DISTINCT_ESTIMATE

An aggregate function. Returns an estimate of the number of distinct values for one or more HyperLogLog states.

Syntax

APPROX_COUNT_DISTINCT_ESTIMATE ( expr )

Arguments

expr

An expression evaluating to a scalar value of type VARBINARY(16384). This scalar value is the HyperLogLog state for which APPROX_COUNT_DISTINCT_ESTIMATE returns the number of distinct values.

expr may be the name of a column. In this case, APPROX_COUNT_DISTINCT_ESTIMATE combines values in the column (which are HyperLogLog states) and returns the number of distinct values in the combined state.

Remarks

This function is used in conjuction with APPROX_COUNT_DISTINCT_ACCUMULATE and APPROX_COUNT_DISTINCT_COMBINE. To best understand its usage, see the topic Distinct Count Estimation Functions.

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