quantileDD | ClickHouse Docs

Introduced in: v24.1.0

Computes an approximate quantile of a sample with relative-error guarantees. It works by building a DD.

Syntax

quantileDD(relative_accuracy, [level])(expr)

Arguments

expr — Expression over the column values resulting in numeric data types, Date or DateTime. (U)Int* or Float* or Date or DateTime

Returned value

Approximate quantile of the specified level. For Date and DateTime inputs the output format matches the input format. Float64 or Date or DateTime

Examples

Computing quantile with DD sketch

CREATE TABLE example_table (a UInt32, b Float32) ENGINE = Memory;
INSERT INTO example_table VALUES (1, 1.001), (2, 1.002), (3, 1.003), (4, 1.004);

SELECT quantileDD(0.01, 0.75)(a), quantileDD(0.01, 0.75)(b) FROM example_table;

┌─quantileDD(0.01, 0.75)(a)─┬─quantileDD(0.01, 0.75)(b)─┐
│        2.9742334234767016 │                      1.01 │
└───────────────────────────┴───────────────────────────┘