nested mysqli_query gives no results back - php

Question

In this code below I need to echo the result of the subquery.
When I echo $row['email'].'<br>'; the echo works okay and I get all the emails.
Problem is that this:
$resultsub.echo $rowb["email"];
is empty
Question: what do I do wrong in the subquery: $resultsub?
$result = mysqli_query($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

I think you somehow messed your if-else and while parts up. If I "pretty-print" your code snippet above it looks like this (see my comments):
<?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";
}
?>

Answer 2

Why you don't use INNER JOIN query?
See the example below:
$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";
}
Ps. Put all columns that you need in the SQL Statement.
My bests