uniqExact

Introduced in: v1.1.0 Calculates the exact number of different argument values.

The uniqExact function uses more memory than uniq, because the size of the state has unbounded growth as the number of different values increases. Use the uniqExact function if you absolutely need an exact result. Otherwise use the uniq function.

Syntax

uniqExact(x[, ...])

Arguments

x — The function takes a variable number of parameters. Tuple(T) or Array(T) or Date or DateTime or String or (U)Int* or Float* or Decimal

Returned value Returns the exact number of different argument values as a UInt64. UInt64 Examples Basic usage

Query

CREATE TABLE example_data
(
    id UInt32,
    category String
)
ENGINE = Memory;

INSERT INTO example_data VALUES
(1, 'A'), (2, 'B'), (3, 'A'), (4, 'C'), (5, 'B'), (6, 'A');

SELECT uniqExact(category) as exact_unique_categories
FROM example_data;

Response

┌─exact_unique_categories─┐
│                       3 │
└─────────────────────────┘

Multiple arguments

Query

SELECT uniqExact(id, category) as exact_unique_combinations
FROM example_data;

Response

┌─exact_unique_combinations─┐
│                         6 │
└───────────────────────────┘

See Also

​uniqExact

uniqExact