Mark Byers

做矩阵的转置 mat :

>>> [list(row) for row in zip(*mat)]
[[1, 4, 7], [2, 5, 8], [3, 6, 9]]

如果性能是一个问题,您应该了解数据库索引。虽然索引不是sql标准的一部分,但几乎所有数据库都支持索引以帮助提高性能。

我建议您为所有用户的帖子创建一个表,然后向该表添加索引以提高搜索性能。例如,可以在 user 列,以便您可以快速查找给定用户的所有文章。根据应用程序的要求,您可能还需要考虑添加其他索引。

能够输入一些代码并返回结果 立即 .

(免责声明:我经常使用C和python,我认为两者都有各自的优点和缺点。)

您需要一个完整的外部连接,但不幸的是,MySQL不支持这种连接。幸运的是,通过使用 UNION ALL :

更新:更改查询以回答OP更新的问题。

SELECT
    COALESCE(school_day, college_day) AS day,
    COALESCE(school_open_time, college_open_time) AS school_open_time,
    COALESCE(school_close_time, college_close_time) AS school_close_time,
    COALESCE(college_open_time, school_open_time) AS college_open_time,
    COALESCE(college_close_time, school_close_time) AS college_close_time
FROM (
    SELECT * FROM table_school LEFT JOIN table_college ON school_day = college_day
    UNION ALL
    SELECT * FROM table_school RIGHT JOIN table_college ON school_day = college_day
    WHERE school_day IS NULL
) AS T1