ClickHouse/docs/en/sql-reference/aggregate-functions/reference/groupbitmap.md

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groupBitmap

Bitmap or Aggregate calculations from a unsigned integer column, return cardinality of type UInt64, if add suffix -State, then return bitmap object.

groupBitmap(expr)

Arguments

expr – An expression that results in UInt* type.

Return value

Value of the UInt64 type.

Example

Test data:

UserID
1
1
2
3

Query:

SELECT groupBitmap(UserID) as num FROM t

Result:

num
3