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1.6 KiB
1.6 KiB
slug | sidebar_position | title |
---|---|---|
/en/sql-reference/aggregate-functions/reference/uniqthetasketch | 195 | uniqTheta |
Calculates the approximate number of different argument values, using the Theta Sketch Framework.
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-type number.
Implementation details
Function:
-
Calculates a hash for all parameters in the aggregate, then uses it in calculations.
-
Uses the KMV 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 for detail.
See Also