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An aggregate function. Merges two or more HyperLogLog states into a new state and returns a value of type VARBINARY(16384)
representing the new state.
APPROX_COUNT_DISTINCT_COMBINE ( expr )
expr
An expression evaluating to a scalar value of type VARBINARY(16384)
.
expr
is typically the name of a column. In this case, APPROX_COUNT_DISTINCT_COMBINE
uses values in the column (which are HyperLogLog states) to create a new state.
This function is used in conjunction with APPROX_COUNT_DISTINCT_ACCUMULATE
and APPROX_COUNT_DISTINCT_ESTIMATE
. To best understand its usage, see the topic Distinct Count Estimation Functions.