PostgresQL SQL：将结果转换为数组

Question

下面的查询：

    SELECT  i_adgroup_id, i_category_id
    FROM adgroupcategories_br
    WHERE i_adgroup_id IN
    (
        SELECT i_adgroup_id
        FROM adgroupusers_br
        WHERE i_user_id = 103713
    )
    GROUP BY i_adgroup_id, i_category_id;

给我这样的结果：

    i_adgroup_id integer | i_category_id smallint
    ---------------------|-----------------------
    15938                | 2
    15938                | 3
    15938                | 4
    15942                | 1
    15942                | 2

我想要的是这样的结果：

    i_adgroup_id integer | i_category_id smallint[]
    ---------------------|-----------------------
    15938                | { 2, 3, 4 }
    15942                | { 1, 2 }

如何更改原始SQL查询以得到上面的结果？

Answer 1

您要使用array_agg，这应该可以工作：

SELECT i_adgroup_id, array_agg(i_category_id)
FROM adgroupcategories_br
WHERE i_adgroup_id IN
(
    SELECT i_adgroup_id
    FROM adgroupusers_br
    WHERE i_user_id = 103713
)
GROUP BY i_adgroup_id;

请注意，i_category_id不再存在，GROUP BY因为它正在聚合。