mysql - 将我的两个查询优化为一个

Question

我有两张表，一张用于跟踪聊天统计数据，一张用于跟踪邮件统计数据。

我当前的查询是这样的:

SELECT COUNT(id) as chat_amount, DATE_FORMAT(timestamp, '%b %e') as period FROM tblChats WHERE timestamp BETWEEN '{$start}' AND '{$end}' AND UserID = 0 GROUP BY DAY(timestamp) DESC, MONTH(timestamp) DESC, YEAR(timestamp) DESC

SELECT COUNT(id) as mail_amount, DATE_FORMAT(timestamp, '%b %e') as period FROM tblMails WHERE timestamp BETWEEN '{$start}' AND '{$end}' AND UserID = 0 GROUP BY DAY(timestamp) DESC, MONTH(timestamp) DESC, YEAR(timestamp) DESC

我想将这两个查询合并为一个，以便返回的数据如下所示:

Array ( 
[0] => Array ( 
    [period] => 2012-11-09 
    [chat_amount] => 1500 
    [mail_amount] => 100 
) 
[1] => Array ( 
    [period] => 2012-11-08 
    [chat_amount] => 500 
    [mail_amount] => 350 
) 
[2] => Array ( 
    [period] => 2012-11-07 
    [chat_amount] => 2000 
    [mail_amount] => 1300 
) 
[3] => Array ( 
    [period] => 2012-11-06 
    [chat_amount] => 1000 
    [mail_amount] => 970 
) 

)

我怎样才能实现这样的目标？提前谢谢你。

Answer 1

虽然 Saharsh 的回答似乎以您想要的格式为您提供了结果 - 这是一个非常昂贵的查询。

由于您将预期输出引用为序列化的 PHP 数组，这意味着您正在使用 PHP 来处理数据。一种更有效的方法是使用以下查询，然后将数据合并到一个 PHP 数组中:

 SELECT rtype, DATE_FORMAT(iperiod, '%b %e') AS period, amount
 FROM
 (SELECT 'chat' AS rtype,
   COUNT(id) as amount, 
   DATE(timestamp) as iperiod 
   FROM tblChats 
   WHERE timestamp BETWEEN '{$start}' AND '{$end}' 
   AND UserID = 0 
   GROUP BY DATE(timestamp)
 UNION
   SELECT 'mail' as rtype, 
   COUNT(id) as mail_amount, 
   DATE(timestamp) as iperiod 
   FROM tblMails 
   WHERE timestamp BETWEEN '{$start}' AND '{$end}' 
   AND UserID = 0 
 GROUP BY DATE(timestamp)) ilv
 ORDER BY period DESC;

顺便说一句:DATE_FORMAT(timestamp, '%b %e') 不会生成 '2012-11-09'，DESC 修饰符是否适用于 GROUP BY 表达式？