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69 lines
2.7 KiB
Markdown
69 lines
2.7 KiB
Markdown
---
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slug: /en/sql-reference/aggregate-functions/reference/quantiledeterministic
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sidebar_position: 206
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---
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# quantileDeterministic
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Computes an approximate [quantile](https://en.wikipedia.org/wiki/Quantile) of a numeric data sequence.
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This function applies [reservoir sampling](https://en.wikipedia.org/wiki/Reservoir_sampling) with a reservoir size up to 8192 and deterministic algorithm of sampling. The result is deterministic. To get an exact quantile, use the [quantileExact](../../../sql-reference/aggregate-functions/reference/quantileexact.md#quantileexact) function.
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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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quantileDeterministic(level)(expr, determinator)
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```
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Alias: `medianDeterministic`.
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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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- `determinator` — Number whose hash is used instead of a random number generator in the reservoir sampling algorithm to make the result of sampling deterministic. As a determinator you can use any deterministic positive number, for example, a user id or an event id. If the same determinator value occurs too often, the function works incorrectly.
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**Returned value**
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- Approximate 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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┌─val─┐
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│ 1 │
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│ 1 │
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│ 2 │
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│ 3 │
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└─────┘
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```
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Query:
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``` sql
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SELECT quantileDeterministic(val, 1) FROM t
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```
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Result:
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``` text
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┌─quantileDeterministic(val, 1)─┐
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│ 1.5 │
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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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