根據時間戳字段的年齡對MySQL查詢進行排序

Question

對於以下查詢，我訂購了ORDER BY s.points DESC，它工作正常。但我想改變它，所以它的訂單由s.points降序而s.datesubmitted是在最後一小時內。字段s.datesubmitted是一個時間戳。否則，我想按most_recent降序排列。

我該怎麼做？

由於提前，

約翰

$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

我會用最新的功能，如子/加等（MySQL的函數） 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"; 

我無處可考它雖然。

Answer 2

MySQL允許ORDER BY子句中的表達式。

... 
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; 

如果像我懷疑，你真正想要的最後一小時的第一個，然後將不同的排序下的陳舊的人，這個人之前添加另一個ORDER BY變量，

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

和排序DESC也是如此。