Echo two SQL query results on a table - mysql

Question

I have the following code:
<?php
include_once '../includes/db.inc.php';
$sql = "SELECT * FROM clients ORDER BY nif_id ASC;";
$result = mysqli_query($conn, $sql);
$resultCheck = mysqli_num_rows($result);
if ($resultCheck > 0) {
while ($row = mysqli_fetch_assoc($result)) {
$first = $row["prm_nome"];
$last = $row["apelido"];
$phone = $row['nmr_tlm'];
$email = $row['mail'];
$nif = $row['nif_id'];
$flight = "SELECT flight_id FROM flights INNER JOIN clients ON flights.nif_id=clients.nif_id";
echo '<tr>';
echo '<td>'.$nif.'</td>';
echo '<td>'.$first.'</td>';
echo '<td>'.$last.'</td>';
echo '<td>'.$phone.'</td>';
echo '<td>'.$email.'</td>';
echo '<td>'.$flight.'</td>';
echo '</tr>';
}
}
?>
I need to echo the result of the SELECT flight_id FROM flights INNER JOIN clients ON flights.nif_id=clients.nif_id query. But when I save the file, what I get on the page is a link with that query instead of the result.
Should I start a new $sql = with that query under the first $sql =?
Or is there other way?
I tried UNION and SELECT *, flight_id FROM flights INNER JOIN clients ON flights.nif_id=clients.nif_id FROM clients ORDER BY nif_id ASC; but then I get mysqli_num_rows() expects parameter 1 to be mysqli_result, bool given.

Answer 1

You don't need two queries. Just use the joined query.
<?php
include_once '../includes/db.inc.php';
$sql = "SELECT c.prm_nome, c.apelido, c.nmr_tlm, c.mail, c.nif_id, f.flight_id
FROM clients c
JOIN flights f ON f.nif_id = c.nif_id
ORDER BY c.nif_id ASC;";
$result = mysqli_query($conn, $sql) or die(mysqli_error($conn));
$resultCheck = mysqli_num_rows($result);
if ($resultCheck > 0) {
while ($row = mysqli_fetch_assoc($result)) {
$first = $row["prm_nome"];
$last = $row["apelido"];
$phone = $row['nmr_tlm'];
$email = $row['mail'];
$nif = $row['nif_id'];
$flight = $row['flight_id'];
echo '<tr>';
echo '<td>'.$nif.'</td>';
echo '<td>'.$first.'</td>';
echo '<td>'.$last.'</td>';
echo '<td>'.$phone.'</td>';
echo '<td>'.$email.'</td>';
echo '<td>'.$flight.'</td>';
echo '</tr>';
}
}
?>