def nosort process distinctapprox(value: text ): number
def nosort process distinctapprox(value: number): number
Returns an approximate count of distinct values in a group.
value: values to count per group.
Examples
table T = with
[| as Group, as Value |]
[| "A", 1 |]
[| "A", 1 |]
[| "A", 2 |]
[| "B", 2 |]
[| "B", 3 |]
table G[g] = by T.Group
G.Count = distinctapprox(T.Value)
show table "Distinct approx" with
g as "Group"
G.Count as "Count"
This produces the following table:
Group
Count
A
2
B
2
Remarks
distinctapprox is designed for large groups and uses a probabilistic
approximation internally; for small groups, it often matches distinct.