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 )
An expression evaluating to a scalar value of type
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.