Question

对于下面的查询，我按ORDER BY s.points DESC订购，这工作正常。但我想更改它，以便s.points仅在s.datesubmitted在最后一小时内降序。字段s.datesubmitted是时间戳。否则，我想按most_recent降序排序。

我怎么能这样做？

提前致谢，

约翰

 $sqlStr = "SELECT s.loginid, s.title, s.url, s.displayurl, s.points, s.datesubmitted, l.username,
           s.submissionid, s.subcheck, s.topten, COUNT(c.commentid) countComments, 
           GREATEST(s.datesubmitted, COALESCE(MAX(c.datecommented), s.datesubmitted)) AS most_recent
      FROM submission s
      JOIN login l ON s.loginid = l.loginid
 LEFT JOIN comment c ON s.submissionid = c.submissionid
  GROUP BY s.submissionid
  ORDER BY s.points DESC 

     LIMIT $offset, $rowsperpage";

Answer 1

我会使用日期函数，如sub / add等。（mysql函数） http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_datediff

$sqlStr = "SELECT s.loginid, s.title, s.url, s.displayurl, s.points, s.datesubmitted, l.username,
           s.submissionid, s.subcheck, s.topten, COUNT(c.commentid) countComments, 
           GREATEST(s.datesubmitted, COALESCE(MAX(c.datecommented), s.datesubmitted)) AS most_recent
      FROM submission s
      JOIN login l ON s.loginid = l.loginid
 LEFT JOIN comment c ON s.submissionid = c.submissionid
  GROUP BY s.submissionid

  ORDER BY s.points DESC, s.datesubmitted DESC
     WHERE s.datesubmitted > DATE_SUB(NOW(), INTERVAL 1 HOUR)

     LIMIT $offset, $rowsperpage";

我无处可测试它。

Answer 2

MySQL允许ORDER BY子句中的表达式。

...
ORDER BY (CASE WHEN s.submitted > DATE_SUB(NOW(), INTERVAL 1 HOUR) 
  THEN s.points ELSE GREATEST(s.datesubmitted, 
                        COALESCE(MAX(c.datecommented), s.datesubmitted)) END) DESC;

如果我怀疑你真的想要最后一小时的第一个小时，然后是不同排序的陈旧小时，请在此之前添加另一个ORDER BY变量，

(CASE WHEN s.submitted > DATE_SUB(NOW(), INTERVAL 1 HOUR) THEN 1 ELSE 0 END)

并对DESC进行排序。

根据时间戳字段的年龄来排序MySQL查询

2 个答案: