嵌套的mysqli_query沒有返回結果

Question

在下面的這段代碼中，我需要回顯子查詢的結果。 當我回顯$row['email'].'<br>'; 回聲正常，我收到了所有電子郵件。

問題是：

$resultsub.echo $rowb["email"];

是空的

問題：在子查詢$ resultsub中我該怎么做？

$result = mysqli_query($conn, "SELECT * FROM wp_mm_email_bounces");

if ($result) {
// output data of each row
while( $row = mysqli_fetch_assoc( $result ) )
        {
            echo $row['email'].'<br>'; // echo works okay
            $resultsub =  mysqli_query($conn, "SELECT * FROM `wp_mm_external_emails` WHERE `email` = '". $row['email'] ."' "); 
            // when I echo this subquery it runs ok. but somehow I get an empty
            while( $rowb = mysqli_fetch_assoc( $resultsub) )
            {
                echo $rowb["email"];
        } else {
            echo "0 $resultsub";
            }
} else {
echo "0 results";
}

Answer 1

為什么不使用INNER JOIN查詢？

請參閱以下示例：

$sqlString = "SELECT ebounces.email as bouces_email, ext.email as ext_email FROM wp_mm_email_bounces ebouces INNER JOIN wp_mm_external_emails ext ON ebounces.email = ext.email";
$result = mysqli_query($conn, $sqlString);

if ($result) {
    // output data of each row
    while( $row = mysqli_fetch_assoc( $result ) )
    {
        echo $row['bouces_email'].'<br>'; 
        echo $row["ext_email"];
    }
} 
else {
    echo "0 results";
}

附言 將所需的所有列都放在SQL語句中。

我最好的

Answer 2

我認為您以某種方式弄亂了if-else ， while弄亂了內容。 如果我“漂亮地打印”它上面的代碼片段看起來像這樣（請參閱我的評論）：

<?php
$result = mysqli_query($conn, "SELECT * FROM wp_mm_email_bounces");

if ($result) 
{
    while( $row = mysqli_fetch_assoc( $result ) )
    {
        echo $row['email'].'<br>';
        $resultsub =  mysqli_query($conn, "SELECT * FROM `wp_mm_external_emails` WHERE `email` = '". $row['email'] ."' "); 

        while( $rowb = mysqli_fetch_assoc( $resultsub) )
        {
            echo $rowb["email"];
        } 
        else //Where is the corresponding if?
        {
            echo "0 $resultsub";
        }
    }
} //I added this enclosing bracket to the if-statement

else //If this is the corresponding else of your first if at the beginning, then you never closed it
{
    echo "0 results";
}

?>