Mysql 将两个查询优化为一个查询

我有两个表，一个用于跟踪聊天统计信息，另一个用于跟踪邮件统计信息

我当前的查询如下所示：

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

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 
) 

我希望将这两个查询合并为一个查询，以便返回的数据如下所示：

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

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 
) 

)

我怎样才能做到这一点？提前谢谢。

试试这个：

SELECT A.period, chat_amount, mail_amount FROM (
(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) AS A 
LEFT JOIN 
(SELECT COUNT(id) AS mail_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) AS B ON A.period = B.period)
UNION 
SELECT A.period, chat_amount, mail_amount FROM (
(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) AS A 
RIGHT JOIN 
(SELECT COUNT(id) AS mail_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) AS B ON A.period = B.period)

---

虽然Saharsh的答案似乎以您想要的格式为您提供了结果，但这是一个非常昂贵的查询

由于您已将预期输出引用为序列化PHP数组，这意味着您正在使用PHP处理数据。更有效的方法是使用以下查询，然后将数据合并到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_格式（时间戳，%b%e'）不会生成“2012-11-09”，并且DESC修饰符对GROUP BY表达式有效吗？

几乎有效。但是，运行查询会返回相同的邮件金额和聊天金额。对不起，我在表名中输入了一个错误。工作起来很有魅力。谢谢！如果这真的对你有用，那么接受答案并投票表决，我会跟着你。Saharsh的查询确实为我提供了预期的输出，但我非常喜欢您的方法。symcbean，是的，DESC修饰符确实适用于GROUP BY表达式。