php - 如何查找相同列表中的电子邮件？

Question

我有 11 个表 [email1, email2, email3, ... email11]

<?php
$con = mysql_connect("localhost", "root", "");
$db = mysql_select_db("email-db", $con);
$sql = "SELECT Contact_Email FROM email1, email2, email3, email4, email5";
$result = mysql_query($sql);
while ($row = mysql_fetch_array($result)) {
    ?>
    <tr>
        <td><? echo $row['Contact_Email']; ?></td>
        <td><? echo '<br>'; ?></td>
    </tr>
<? } ?>

我实际上想做的是使用 join 从所有表中选择所有电子邮件。怎么做到的？

Answer 1

由于社区投票决定关闭重复 how to display duplicate email address

这是 4 个表的示例，如果需要，您可以将其扩展到 11 个。抱歉，我没有调试这段代码，我猜主要障碍是 mysql 查询从数据库中获取正确的值。

而且您绝对应该停止使用 mysql* 函数!

$sql ="SELECT t.Contact_Email,
  e1.Contact_Email email1,
  e2.Contact_Email email2,
  e3.Contact_Email email3,
  e4.Contact_Email email4
FROM (
SELECT e.Contact_Email FROM email1 e
UNION ALL 
SELECT e.Contact_Email FROM email2 e
UNION ALL 
SELECT e.Contact_Email FROM email3 e
UNION ALL 
SELECT e.Contact_Email FROM email4 e
) t
LEFT JOIN email1 e1
ON t.Contact_Email = e1.Contact_Email
LEFT JOIN email2 e2
ON t.Contact_Email = e2.Contact_Email
LEFT JOIN email3 e3
ON t.Contact_Email = e3.Contact_Email
LEFT JOIN email4 e4
ON t.Contact_Email = e4.Contact_Email";

echo '<table><thead><tr><th>Email</th>';
for ($i=1;$i<5; $i++){
    echo "<th>email $i</th>";
}
echo '</tr></thead><tbody>';

$result = mysql_query($sql);
while ($row = mysql_fetch_array($result)) {
    echo '<tr><td>'.$row['Contact_Email'].'</td>';
    for ($i=1;$i<5; $i++){
        echo '<td>'.(empty($row['email'.$i])?'no':'yes').'</td>';
    }
    echo '</tr>';
}
echo '</tbody></table>';

UPDATE 使用相同的查询，但将输出部分更改为:

echo '<table><thead><tr><th>Email</th>';
for ($i=1;$i<5; $i++){
    echo "<th>email $i</th>";
}
echo "<th>Total (yes)</th>";
echo "<th>Total (no)</th>";
echo '</tr></thead><tbody>';

$result = mysql_query($sql);
while ($row = mysql_fetch_array($result)) {
    $yesCount = 0;
    $noCount = 0;
    echo '<tr><td>'.$row['Contact_Email'].'</td>';
    for ($i=1;$i<5; $i++){
        echo '<td>'.(empty($row['email'.$i])?'no':'yes').'</td>';
        if (empty($row['email'.$i])) {
            $noCount++;
        } else {
            $yesCount++;
        }
    }
    echo '<th>'.$yesCount.'</th>';
    echo '<th>'.$noCount.'</th>';
    echo '</tr>';
}
echo '</tbody></table>';