如何使用连接2次或更多次随机选择2行

Question

我有3张桌子：

  News      |      Categories      |      News_in_cat
   id       |          id          |          id
  title     |         name         |        news_id
            |                      |        cat_id

目标是让mySql从Categories表中选择1个随机类别，然后查看News_in_cat表并从News table中返回选定类别的2个随机新闻。

Answer 1

SELECT * FROM News_in_cat AS nic
(SELECT * FROM categories ORDER BY RAND() limit 1) AS t
ON t.id = nic.cat_id
INNER JOIN News AS n 
ON n.id = nic.news_id
ORDER BY RAND()
LIMIT 2;