How to classify results depending on percentiles at runtime?

If you want to classify each result row in a query based on percentile, you can combine arrayMap and arraySum to classify each row.

WITH (
        SELECT quantiles(0.33, 0.66)(number)
        FROM numbers(10)
    ) AS cuts
SELECT
    number,
    arraySum(arrayMap(x -> (x > number), cuts)) AS t,
    multiIf(t = 0, 'high', t = 1, 'med', t = 2, 'low', 'none') AS c
FROM numbers(10)

Query id: 71952567-ff29-4559-bacc-1d27d5fdacf9

┌─number─┬─t─┬─c────┐
│      0 │ 2 │ low  │
│      1 │ 2 │ low  │
│      2 │ 2 │ low  │
│      3 │ 1 │ med  │
│      4 │ 1 │ med  │
│      5 │ 1 │ med  │
│      6 │ 0 │ high │
│      7 │ 0 │ high │
│      8 │ 0 │ high │
│      9 │ 0 │ high │
└────────┴───┴──────┘

You can set up a materialized view and pull the percentiles from it instead of computing them at runtime.