Question

假设您需要按照左下边界的下降对numranges数组进行排序。以下方法是最简单的：unnest将数组放入表中，对表进行排序，array_agg将其重新放入数组中。怎么看代码？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，以完成aggragate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;
$$;

PostgreSQL：使用一些排序条件对元素数组进行排序

1 个答案: