php - mysql查询从多个中选择，按日期排序

Question

从多个表中进行选择并按日期(从新到旧)对所有内容进行排序的好而简单的方法是什么？

 mysql_query("
               SELECT * 
               FROM posts, comments, photos 
               WHERE userID='$session' 
               ORDER BY date");

如果我想做那样的事情。

Answer 1

SELECT *
FROM (SELECT userID, Col1, Col2, Col3, date
      FROM posts
      UNION
      SELECT userID, Col1, Col2, Col3, date
      FROM comments
      SELECT userID, Col1, Col2, Col3, date
      FROM photos ) t
WHERE userID = 123
ORDER BY date DESC