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countResample

Description​

The Resample combinator can be applied to the count aggregate function to count values of a specified key column in a fixed number of intervals (N).

Example usage​

Basic example​

Let's look at an example. We'll create a table which contains the name, age and wage of employees, and we'll insert some data into it:

CREATE TABLE employee_data 
(
    name String,
    age UInt8,
    wage Float32
) 
ENGINE = MergeTree()
ORDER BY tuple()

INSERT INTO employee_data (name, age, wage) VALUES
    ('John', 16, 10.0),
    ('Alice', 30, 15.0),
    ('Mary', 35, 8.0),
    ('Evelyn', 48, 11.5),
    ('David', 62, 9.9),
    ('Brian', 60, 16.0);

Let's get the average wage of the people whose age lies in the intervals of [30,60) and [60,75) ([ is exclusive and ) is inclusive). Since we use integer representation for age, we get ages in the intervals [30, 59] and [60,74]. To do so we apply the Resample combinator to the avg aggregate function.

WITH avg_wage AS
(
    SELECT avgResample(30, 75, 30)(wage, age) AS original_avg_wage
    FROM employee_data
)
SELECT
    arrayMap(x -> round(x, 3), original_avg_wage) AS avg_wage_rounded
FROM avg_wage;

┌─avg_wage_rounded─┐
│ [11.5,12.95]     │
└──────────────────┘

See also​