PostgreSQL：使用某种排序条件对元素数组进行排序

Question

假设您需要按左边界降序对 numranges 的数组进行排序。下面的做法是不是最简单的：unnest数组变成了table，排序后table，array_agg又变成了数组。这在代码中看起来如何？这是我的非工作尝试：

DO $$
DECLARE
    x numrange[] := '{"[0, 3]", "[0, 1]", "[3, 5]", "[3, 8]"}';
BEGIN

    x := (
          WITH x AS (
              SELECT xrow FROM unnest(x) AS xrow
          )
          SELECT array_agg(xrow) FROM x ORDER BY lower(xrow) DESC
    );
    RAISE NOTICE '%', x;
END;
$$;

Answer 1

您必须将 ORDER BY 移动到聚合函数中，以影响聚合顺序，请参阅 manual:

DO $$
DECLARE
    x numrange[] := '{"[0, 3]", "[0, 1]", "[3, 5]", "[3, 8]"}';
BEGIN

    x := (WITH x AS (
            SELECT xrow FROM unnest(x) AS xrow
        )
        SELECT array_agg(xrow  ORDER BY lower(xrow) DESC) FROM x

    );
    RAISE NOTICE '%', x;
END;
$$;