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对数组进行分组和计数

clickhouse

0

fl00r · 技术社区 · 7 年前

arrayReduce 不适用于任意的lambda。有没有办法计算数组中元素的出现次数?就像

select groupArray(age) from customers;
:) [21, 40, 20, 20, 20, 30]
select arrayReduce('groupUniqArray', groupArray(age)) from customers;
:) [21, 40, 20, 30]
select arrayReduce('???', groupArray(age)) from customers;
:) [(21, 1), (40, 1), (20, 3), (30, 1)]

输出格式没有那么重要。我不想在这里使用groupby/count,因为我想用一个查询聚合多个字段。

select 
  arrayReduce('???', groupArray(age)),
  arrayReduce('???', groupArray(job)),
  arrayReduce('???', groupArray(country))
from customers;

0 回复 | 直到 7 年前

1

vladimir 7 年前

只需进行几次数组操作:

SELECT
    groupArray(age) AS ages,
    arrayReduce('groupUniqArray', ages) AS uniqAges,
    arraySort(x -> x.1, arrayMap(x -> (x, countEqual(ages, x)), uniqAges)) AS resultAges,

    groupArray(job) AS jobs,
    arrayReduce('groupUniqArray', jobs) AS uniqJobs,
    arraySort(x -> x.1, arrayMap(x -> (x, countEqual(jobs, x)), uniqJobs)) AS resultJobs,

    groupArray(country) AS countries,
    arrayReduce('groupUniqArray', countries) AS uniqCountries,
    arraySort(x -> x.1, arrayMap(x -> (x, countEqual(countries, x)), uniqCountries)) AS resultCountries
FROM test.test4
FORMAT Vertical