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> Computes an approximate quantile of a numeric data sequence.

# quantile

<h2 id="quantile">
  quantile
</h2>

Introduced in: v1.1.0

Computes an approximate [`quantile`](https://en.wikipedia.org/wiki/Quantile) of a numeric data sequence.

This function applies [reservoir sampling](https://en.wikipedia.org/wiki/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`](/reference/functions/aggregate-functions/quantileExact#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`](/reference/functions/aggregate-functions/quantiles#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**

```sql theme={null}
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`](/reference/data-types/float)

**Arguments**

* `expr` — Expression over the column values resulting in numeric data types, Date or DateTime. [`(U)Int*`](/reference/data-types/int-uint) or [`Float*`](/reference/data-types/float) or [`Decimal*`](/reference/data-types/decimal) or [`Date`](/reference/data-types/date) or [`DateTime`](/reference/data-types/datetime)

**Returned value**

Approximate quantile of the specified level. [`Float64`](/reference/data-types/float) or [`Date`](/reference/data-types/date) or [`DateTime`](/reference/data-types/datetime)

**Examples**

**Computing quantile**

```sql title=Query theme={null}
CREATE TABLE t (val UInt32) ENGINE = Memory;
INSERT INTO t VALUES (1), (1), (2), (3);

SELECT quantile(val) FROM t;
```

```response title=Response theme={null}
┌─quantile(val)─┐
│           1.5 │
└───────────────┘
```

**See Also**

* [median](/reference/functions/aggregate-functions/median)
* [quantiles](/reference/functions/aggregate-functions/quantiles)