PHP If Else Not working like i thought it would - php

Question

Ok i am very stuck here and i am might be looking at this completely wrong (still kind of a newbie) or super close just missing something small i cant tell.
At the bottom here you will find my code with a If ElseIf Else statement. That i just cant get to do what i want. so i am hoping someone can help guide me in the right direction.
On the If it checks to make sure that the promocode that was entered is in the database and that part works.
on the elseif i want it to look through the database and find the promocode and confirm that there isnt an email address associated with that promocode. The way that it is below with the IS NOT NULL in the query works for when there is an email address in that promocode but when there isnt anything for that promocode it is still saying that there is and gives the submit data of today but i can assure that there isnt anything in the database.
This is where my problem lies am i doing this completely wrong is there a better way to accomplish what i am trying to do here? Or have i just overlooked something small?
$promosql = "SELECT * FROM formdata WHERE (promoCode = '$varPromo')";
$promoraw = $mysqli->query($promosql);
$dupesql = "SELECT * FROM formdata WHERE (promoCode = '$varPromo' AND email IS NOT NULL)";
$duperaw = $mysqli->query($dupesql);
if($promoraw->num_rows <> 1) {
//echo ("$varName already exists in $varAddress \n");
$promo .= "$varPromo is not a valid promocode \n";
}
elseif($duperaw->num_rows > 0) {
//echo ("$varName already exists in $varAddress \n");
$dupe .= "$varPromo has already been used on $varDate \n";
}
else {
$sql = "INSERT INTO formdata (promoCode, name, email, address, city, state, zip, submitDate) VALUES (".
PrepSQL($varPromo) . ", " .
PrepSQL($varName) . ", " .
PrepSQL($varEmail) . ", " .
PrepSQL($varAddress) . ", " .
PrepSQL($varCity) . ", " .
PrepSQL($varState) . ", " .
PrepSQL($varZip) . ", " .
PrepSQL($varDate) . ")";
$mysqli->query($sql);
header("location: index.php?success=1");
exit();
}

Answer 1

Try this query:
SELECT email IS NULL or email = '' has_email FROM formdata WHERE promoCode = '$varPromo'
Then your PHP can do:
if ($promoraw->nul_rows == 0) {
// Not a valid promo code
} else {
$row = $promoraw->fetch_assoc();
if ($row['has_email']) {
// Promo code has been used
} else {
// Insert into table
}
}