ClickHouse/docs/en/sql-reference/aggregate-functions/reference/uniqthetasketch.md

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# uniqTheta

Calculates the approximate number of different argument values, using the [Theta Sketch Framework](https://datasketches.apache.org/docs/Theta/ThetaSketchFramework.html).

``` sql
uniqTheta(x[, ...])
```

**Arguments**

The function takes a variable number of parameters. Parameters can be `Tuple`, `Array`, `Date`, `DateTime`, `String`, or numeric types.

**Returned value**

-   A [UInt64](../../../sql-reference/data-types/int-uint.md)-type number.

**Implementation details**

Function:

-   Calculates a hash for all parameters in the aggregate, then uses it in calculations.

-   Uses the [KMV](https://datasketches.apache.org/docs/Theta/InverseEstimate.html) algorithm to approximate the number of different argument values.

        4096(2^12) 64-bit sketch are used. The size of the state is about 41 KB.

-   The relative error is 3.125% (95% confidence), see the [relative error table](https://datasketches.apache.org/docs/Theta/ThetaErrorTable.html) for detail.

**See Also**

-   [uniq](../../../sql-reference/aggregate-functions/reference/uniq.md#agg_function-uniq)
-   [uniqCombined](../../../sql-reference/aggregate-functions/reference/uniqcombined.md#agg_function-uniqcombined)
-   [uniqCombined64](../../../sql-reference/aggregate-functions/reference/uniqcombined64.md#agg_function-uniqcombined64)
-   [uniqHLL12](../../../sql-reference/aggregate-functions/reference/uniqhll12.md#agg_function-uniqhll12)
-   [uniqExact](../../../sql-reference/aggregate-functions/reference/uniqexact.md#agg_function-uniqexact)