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2.8 KiB
Markdown
69 lines
2.8 KiB
Markdown
---
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slug: /en/sql-reference/aggregate-functions/reference/quantileexactweighted
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sidebar_position: 174
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---
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# quantileExactWeighted
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Exactly computes the [quantile](https://en.wikipedia.org/wiki/Quantile) of a numeric data sequence, taking into account the weight of each element.
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To get exact value, all the passed values are combined into an array, which is then partially sorted. Each value is counted with its weight, as if it is present `weight` times. A hash table is used in the algorithm. Because of this, if the passed values are frequently repeated, the function consumes less RAM than [quantileExact](../../../sql-reference/aggregate-functions/reference/quantileexact.md#quantileexact). You can use this function instead of `quantileExact` and specify the weight 1.
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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](../../../sql-reference/aggregate-functions/reference/quantiles.md#quantiles) function.
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**Syntax**
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``` sql
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quantileExactWeighted(level)(expr, weight)
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```
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Alias: `medianExactWeighted`.
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**Arguments**
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- `level` — Level of quantile. Optional parameter. 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](https://en.wikipedia.org/wiki/Median).
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- `expr` — Expression over the column values resulting in numeric [data types](../../../sql-reference/data-types/index.md#data_types), [Date](../../../sql-reference/data-types/date.md) or [DateTime](../../../sql-reference/data-types/datetime.md).
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- `weight` — Column with weights of sequence members. Weight is a number of value occurrences with [Unsigned integer types](../../../sql-reference/data-types/int-uint.md).
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**Returned value**
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- Quantile of the specified level.
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Type:
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- [Float64](../../../sql-reference/data-types/float.md) for numeric data type input.
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- [Date](../../../sql-reference/data-types/date.md) if input values have the `Date` type.
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- [DateTime](../../../sql-reference/data-types/datetime.md) if input values have the `DateTime` type.
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**Example**
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Input table:
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``` text
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┌─n─┬─val─┐
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│ 0 │ 3 │
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│ 1 │ 2 │
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│ 2 │ 1 │
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│ 5 │ 4 │
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└───┴─────┘
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```
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Query:
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``` sql
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SELECT quantileExactWeighted(n, val) FROM t
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```
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Result:
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``` text
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┌─quantileExactWeighted(n, val)─┐
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│ 1 │
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└───────────────────────────────┘
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```
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**See Also**
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- [median](../../../sql-reference/aggregate-functions/reference/median.md#median)
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- [quantiles](../../../sql-reference/aggregate-functions/reference/quantiles.md#quantiles)
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