ClickHouse/docs/en/sql-reference/functions/uniqtheta-functions.md

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/en/sql-reference/functions/uniqtheta-functions	210	uniqTheta

uniqTheta Functions

uniqTheta functions work for two uniqThetaSketch objects to do set operation calculations such as ∪ / ∩ / × (union/intersect/not), it is to return a new uniqThetaSketch object contain the result.

A uniqThetaSketch object is to be constructed by aggregation function uniqTheta with -State.

UniqThetaSketch is a data structure storage of approximate values set. For more information on RoaringBitmap, see: Theta Sketch Framework.

uniqThetaUnion

Two uniqThetaSketch objects to do union calculation(set operation ∪), the result is a new uniqThetaSketch.

uniqThetaUnion(uniqThetaSketch,uniqThetaSketch)

Arguments

• uniqThetaSketch – uniqThetaSketch object.

Example

select finalizeAggregation(uniqThetaUnion(a, b)) as a_union_b, finalizeAggregation(a) as a_cardinality, finalizeAggregation(b) as b_cardinality
from
(select arrayReduce('uniqThetaState',[1,2]) as a, arrayReduce('uniqThetaState',[2,3,4]) as b );

┌─a_union_b─┬─a_cardinality─┬─b_cardinality─┐
│         4 │             2 │             3 │
└───────────┴───────────────┴───────────────┘

uniqThetaIntersect

Two uniqThetaSketch objects to do intersect calculation(set operation ∩), the result is a new uniqThetaSketch.

uniqThetaIntersect(uniqThetaSketch,uniqThetaSketch)

Arguments

• uniqThetaSketch – uniqThetaSketch object.

Example

select finalizeAggregation(uniqThetaIntersect(a, b)) as a_intersect_b, finalizeAggregation(a) as a_cardinality, finalizeAggregation(b) as b_cardinality
from
(select arrayReduce('uniqThetaState',[1,2]) as a, arrayReduce('uniqThetaState',[2,3,4]) as b );

┌─a_intersect_b─┬─a_cardinality─┬─b_cardinality─┐
│             1 │             2 │             3 │
└───────────────┴───────────────┴───────────────┘

uniqThetaNot

Two uniqThetaSketch objects to do a_not_b calculation(set operation ×), the result is a new uniqThetaSketch.

uniqThetaNot(uniqThetaSketch,uniqThetaSketch)

Arguments

• uniqThetaSketch – uniqThetaSketch object.

Example

select finalizeAggregation(uniqThetaNot(a, b)) as a_not_b, finalizeAggregation(a) as a_cardinality, finalizeAggregation(b) as b_cardinality
from
(select arrayReduce('uniqThetaState',[2,3,4]) as a, arrayReduce('uniqThetaState',[1,2]) as b );

┌─a_not_b─┬─a_cardinality─┬─b_cardinality─┐
│       2 │             3 │             2 │
└─────────┴───────────────┴───────────────┘

See Also

• uniqThetaSketch