quantile

Introduced in: v1.1

Computes an approximate quantile of a numeric data sequence.

This function applies reservoir sampling with a reservoir size up to 8192 and a random number generator for sampling. The result is non-deterministic. To get an exact quantile, use the quantileExact function.

When using multiple quantile* functions with different levels in a query, the internal states are not combined (that is, the query works less efficiently than it could). In this case, use the quantiles function.

Note that for an empty numeric sequence, quantile will return NaN, but its quantile* variants will return either NaN or a default value for the sequence type, depending on the variant.

Syntax

quantile(level)(expr)

Aliases: median

Parameters

level — Optional. Level of quantile. Constant floating-point number from 0 to 1. We recommend using a level value in the range of [0.01, 0.99]. Default value: 0.5. At level=0.5 the function calculates median. Float

Arguments

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

Returned value

Approximate quantile of the specified level. Float64 or Date or DateTime

Examples

Computing quantile

CREATE TABLE t (val UInt32) ENGINE = Memory;
INSERT INTO t VALUES (1), (1), (2), (3);

SELECT quantile(val) FROM t;

┌─quantile(val)─┐
│           1.5 │
└───────────────┘

See Also

quantile​

quantile