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41 lines
1.4 KiB
Markdown
41 lines
1.4 KiB
Markdown
---
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toc_priority: 190
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---
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# uniq {#agg_function-uniq}
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Calculates the approximate number of different values of the argument.
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``` sql
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uniq(x[, ...])
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```
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**Parameters**
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The function takes a variable number of parameters. Parameters can be `Tuple`, `Array`, `Date`, `DateTime`, `String`, or numeric types.
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**Returned value**
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- A [UInt64](../../../sql-reference/data-types/int-uint.md)-type number.
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**Implementation details**
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Function:
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- Calculates a hash for all parameters in the aggregate, then uses it in calculations.
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- Uses an adaptive sampling algorithm. For the calculation state, the function uses a sample of element hash values up to 65536.
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This algorithm is very accurate and very efficient on the CPU. When the query contains several of these functions, using `uniq` is almost as fast as using other aggregate functions.
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- Provides the result deterministically (it doesn’t depend on the query processing order).
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We recommend using this function in almost all scenarios.
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**See Also**
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- [uniqCombined](../../../sql-reference/aggregate-functions/reference/uniqcombined.md#agg_function-uniqcombined)
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- [uniqCombined64](../../../sql-reference/aggregate-functions/reference/uniqcombined64.md#agg_function-uniqcombined64)
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- [uniqHLL12](../../../sql-reference/aggregate-functions/reference/uniqhll12.md#agg_function-uniqhll12)
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- [uniqExact](../../../sql-reference/aggregate-functions/reference/uniqexact.md#agg_function-uniqexact)
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