是否需要先按 2 列分组，再按 1 列分组进行 2 次查询？

Question

我有一个包含电子邮件地址的表（列：id、电子邮件、用户、日期）。我正在尝试按日期和用户对电子邮件地址进行求和，我可以使用下面的代码来完成此操作；但随后还要对所有用户的总数进行求和并将其显示在该日期下方。我不知道该怎么做...我需要再做一次查询来计算每个日期的总计吗？

$sql = mysql_query("SELECT date, COUNT(email), user FROM emails GROUP BY DATE(date), user");
while ($row = mysql_fetch_array($sql)){
  echo date('m/d', strtotime($row['date'])) . " " . $row['user'] . " " . $row['COUNT(email)'] . "<br />";
}

我拥有什么：

date user count(email)
09/09 29 8
09/09 49 9
09/10 29 4
09/10 49 13
09/11 29 1
09/11 49 3

我想要什么：

date user count(email)
09/09 29 8
09/09 49 9
09/09 total 17

09/10 29 5
09/10 49 13
09/10 total 18

09/11 29 1
09/11 49 3
09/11 total 4

谢谢

编辑：这是我的有效代码：

$sql = mysql_query("SELECT date, COUNT(email), user FROM emails GROUP BY DATE(date), user WITH ROLLUP");

while ($row = mysql_fetch_array($sql)){
  echo date('m/d', strtotime($row['date'])) . " " . (!isset($row['user']) ? 'total' : $row['user']) . " " . $row['COUNT(email)'] . "<br />";
}

Answer 1

请参阅使用 ROLLUP （GROUP BY 修饰符）。

SELECT DATE(`date`) AS date
     , user 
     , COUNT(email) AS cnt
FROM emails 
GROUP BY DATE(`date`)
       , user 
WITH ROLLUP 

会给你：

date    user   cnt
09/09   29       8
09/09   49       9
09/09   NULL    17

09/10   29       5
09/10   49      13
09/10   NULL    18 

09/11   29       1
09/11   49       3
09/11   NULL     4

NULL    NULL    39

Answer 2

我认为你可以使用 UNION ALL 来做到这一点。它是这样的：

SELECT date, COUNT(email), user
FROM emails
GROUP BY DATE(date), user
UNION ALL
SELECT date, COUNT(email), -1
FROM emails
GROUP BY DATE(date)
ORDER date ASC

或者你可以用 PHP 方式：

$previousDate = null;
$total = 0;
$sql = mysql_query("SELECT date, COUNT(email), user FROM emails GROUP BY DATE(date), user");
while ($row = mysql_fetch_array($sql)){
    if ($previousDate != date('m/d', strtotime($row['date']))) {
        echo $previousDate . " total " . $total . "<br /><br />";
        $total = 0;
        $previousDate = date('m/d', strtotime($row['date']));
    }

    echo date('m/d', strtotime($row['date'])) . " " . $row['user'] . " " . $row['COUNT(email)'] . "<br />";
    $total = $total + $row['COUNT(email)'];
}