如何在presto中将列转换为数组

Posted 2023-02-16

【中文标题】如何在presto中将列转换为数组

【英文标题】：how to convert a column to an array in presto

【发布时间】：2021-10-20 23:41:00

【问题描述】：

Postgres 提供了一种将列转换为数组的方法。示例查询：

WITH
    dataset AS (
        SELECT '1' as a
        union
        SELECT '2' as a
        union
        SELECT '3' as a
    )
SELECT
    array(select a from dataset) as array_result;

返回

| array_result |
|--------------|
| 2,3,1      |

如何使用 Presto SQL 做同样的事情？

【参考方案1】：

使用array_agg(x [ORDER BY y])聚合函数：

WITH
    dataset AS (
        SELECT '1' as a
        union all
        SELECT '2' as a
        union all
        SELECT '3' as a
    )
SELECT
    array_agg(a) as array_result from dataset;

结果：

['3', '2', '1']

如果需要array<int>，请在聚合前强制转换：array_agg(cast(a as int))